๐Ÿ’ก The answer in 60 seconds

Want to pay once and read ABS, airbag, TPMS and transmission codes from your phone? BlueDriver: $99.95 (Pro Next-Gen) or $139.95 (Pro), no subscription, on the makes its checker lists.
Want the lowest published price of these four to read and clear the check engine light? FIXD: $59.99 sensor, and the free app reads engine codes, live data and ABS codes on listed makes; the extras are FIXD Premium, $69.99 to $99.99 a year depending on where you buy it.
Own one brand of car and want service functions (oil reset, parking brake, battery)? Autel MaxiAP AP200: all generic OBD2 free, one brand's software free, up to 19 service functions listed, $21.99 a year for each extra listed brand in the App Store; Autel publishes no dongle price and its iPhone app was last updated in 2023.
Want a screen and a cable, no phone, no app, ABS and airbag included? Autel AutoLink AL619, $99.99 on Autel's store.
Hearing a noise with no light? There is no code for a scanner to read; see what a scanner cannot see.

If you searched "BlueDriver vs Autel vs FIXD", you are probably one click from buying. This page reads the three makers' pages for you, with one rule: every product fact comes from the maker's own page, manual, policy or official app-store listing, opened on 30 September 2026, and quoted as printed. Where a maker published nothing, we say so instead of filling the gap.

FIXD vs PulsCar already covers FIXD's prices, trials, Trustpilot profiles and cancellation; we re-read FIXD's pages today for the facts used here and link there rather than repeat it.

The verdict by buyer type

Most "which is better" questions are really "which is better for me". Here is the short version, before any tables.

One payment, enhanced systems, phone app โ€” the Pro lists ABS, airbag (SRS) and TPMS on named makes, plus freeze frame, Mode 6, smog check and repair reports, no subscription ๐ŸŸข
BlueDriver
Lowest published entry price of the four โ€” free app covers codes, clearing, live data, maintenance and recall alerts, ABS on listed makes ๐ŸŸข
FIXD sensor, free app
One brand of car, wants service resets โ€” oil reset, parking brake (EPB), battery (BMS) and more in Autel's list; no Autel price; app rated 2.2 on iPhone and 4.3 on Android ๐ŸŸข
Autel AP200, with caveats
No smartphone, or wants a tool that lives in the trunk โ€” own screen, cable, ABS and SRS codes ๐ŸŸข
Autel AL619
Shopping for a used car โ€” BlueDriver, AP200 and AL619 list readiness; FIXD Premium has Emissions Precheck and vehicle history reports ๐ŸŸข
BlueDriver or Autel
Wants a live mechanic to ask about the result โ€” FIXD Premium's Mechanic Hotline; BlueDriver lists 24/7 support for its product ๐ŸŸข
FIXD Premium
A new noise and no warning light โ€” a scanner reads stored codes, and a sound with no code has none to read; FIXD's free app lists a Manual Diagnostic for issues its sensor cannot detect ๐ŸŸข
No code to read

Which one would we pick for a first-time buyer with one ordinary car, and is PulsCar neutral about that? We are not neutral, since PulsCar's app works with the OBDLink MX+, but we sell none of these three brands. For a single car, bought from the maker, the BlueDriver Pro Next-Gen at $99.95 is the product whose own documents list the widest set of phone-app diagnostics for a published one-time price: engine codes plus ABS, airbag and TPMS on the makes listed on its page, freeze frame, Mode 6, a smog-readiness check and repair reports, with no subscription and a 180-day money-back guarantee. FIXD costs less to start and its free tier is genuinely useful, but its Emissions Precheck and repair cost estimates are in Premium in its FAQ table. Autel's AP200 lists the most service functions of the four, and the AL619 is the only one that works without a phone.

Two caveats on BlueDriver. Its app is rated 4.6 on the App Store and 3.5 on Google Play. And its pages do not spell out what the Pro's extra $40.00 buys over the Next-Gen; each has its own checker, so run the one for the model you are buying.

How we checked, and where the limits are

Everything here was read on 30 September 2026 from the makers themselves: BlueDriver's store, checker, refund policy and support centre; FIXD's homepage, FAQ, features, returns and trial pages; Autel's product pages, its official store, the AP200 and AL619 manuals and its return and warranty pages. Ratings come from the App Store, Apple's public lookup data and Google Play, read the same day. What OBD II is required to do comes from the California Air Resources Board.

๐ŸŸข Published means a maker, Apple, Google or a regulator printed it; the page is in the Sources block. โšช Reported means a platform's own aggregate, such as a star rating. The verdict rows are our reading of those published facts.

What this page cannot tell you: whether any of the four reads your car. That depends on the vehicle, its model year and the market it was first sold in. The section on coverage checkers shows where each maker lets you test that before buying.

The four products, and why these two Autels

BlueDriver and FIXD each sell a small family of consumer sensors, so choosing is easy. BlueDriver's US store lists two consumer sensors, the Pro Next-Gen and the Pro; FIXD's pages show one Bluetooth sensor at $59.99 (its returns page also names a separate FIXD Guardian sensor with a yearly subscription, which this page does not compare). Autel is different: its store lists code readers from under $25 to scan tablets above $1,000, so "Autel" on its own is not a product.

We picked two Autels by the question a reader of this page is actually asking.

The phone-app Autel: MaxiAP AP200. BlueDriver and FIXD are both a small Bluetooth plug plus a phone app, so the fair Autel counterpart is Autel's own plug-plus-app product. Autel's page describes it as a "Smartphone All System Scan Tool App With Bluetooth OBD2 Adapter". Autel's official US store lists no phone-app dongle like it; its Bluetooth-connected diagnostic tools there are screen-based scanners, such as the MaxiDiag MD906 Pro handheld at $299 and the MaxiCOM MK808BT Pro tablet at $549, which is a different purchase altogether. One gap we could not close: Autel does not list the AP200 on store.autel.com, and we found no price for it published by Autel itself, so this page quotes no price for the AP200 dongle. Retail prices vary by seller.

The handheld Autel: AutoLink AL619. Some buyers want a scanner with its own screen and a cable, no phone involved. Autel's store lists the AL619 at $99.99, marked as a limited sale price, which sits in the same band as BlueDriver's $99.95 Pro Next-Gen, and it reads ABS and airbag codes as well as engine codes. Two of its nearest store neighbours are the AutoLink AL519 at $59.99, an OBD II code reader whose page describes all 10 OBD II test modes and a one-click readiness key but lists no ABS or airbag, and the MaxiLink ML629 at $126.88, which adds transmission to engine, ABS and SRS but whose page gives that four-system coverage as "year up to 2014/2015" in one line and 1996 and newer in another. We chose the AL619 because it matches BlueDriver on price and covers the same safety systems a buyer usually asks about next, ABS and airbag.

BlueDriver Pro Next-Gen โ€” Bluetooth sensor plus free app, iPhone and Android; BlueDriver calls it ideal for newer North American vehicles ๐ŸŸข
$99.95
BlueDriver Pro โ€” the original sensor, same app, same no-subscription line ๐ŸŸข
$139.95
FIXD Sensor โ€” Bluetooth Low Energy plug plus free app with an optional paid tier ๐ŸŸข
$59.99
Autel MaxiAP AP200 โ€” Bluetooth dongle plus the MaxiAP200 app; one vehicle brand's software included ๐ŸŸข
price not published
Autel AutoLink AL619 โ€” handheld with colour screen and OBD II cable, engine plus ABS and SRS ๐ŸŸข
$99.99

Price and what is in the box

The sticker price decides least; what the price includes decides more.

BlueDriver. The Pro Next-Gen shows $99.95 against a struck-through $119.95, and the Pro shows $139.95, both on BlueDriver's own US store. The footer of every store page lists free shipping on all orders, a 180-day risk-free return policy and a one-year limited warranty. The product pages sell the sensor; the app is a free download from the App Store or Google Play. The store's line on what the price covers is plain: "No in app fees or add-ons. One purchase gets you everything you need."

FIXD. The FAQ says "Our sensor retails for $59.99", the homepage hero panel shows $59 next to "Free 1 Year Warranty" and "100% Risk Free Money Back Guarantee", and the fixd.com order form shows $59.99 with "*Limit one per household" and a Premium option footnoted "*Free 1 week trial ($5.85/month, billed annually)". Like BlueDriver, FIXD prints no packing list; it sells the sensor and the app is free. The paid layer, FIXD Premium, is where the FIXD price story actually lives, and it is covered in the next section and in full on the FIXD page.

Autel AP200. Autel's page says "The MaxiAP AP200 package includes a Bluetooth (BT) OBDII connector and a MaxiAP200 app." The user manual repeats that and describes the dongle's LED states and its standby mode after more than ten minutes without a phone connection. As noted, Autel does not publish a US price for it on its own store.

Autel AL619. The store page prints a full packing list: the AL619, an OBD II cable, a USB cable, a carry bag, a user manual and a TF card, the memory card Autel uses for data backup and software updates. The price shown is $99.99 with the line "Final price. Tax & shipping included.", labelled a limited-time promotion. It is the only one of the four with its own screen, so there is nothing else to buy or download to start using it.

FIXD Sensor โ€” sensor only; phone required; the paid tier is optional ๐ŸŸข
$59.99
BlueDriver Pro Next-Gen โ€” sensor only; phone required; nothing further to buy ๐ŸŸข
$99.95
Autel AL619 โ€” handheld, cable, USB cable, bag, manual, TF card; tax and shipping included ๐ŸŸข
$99.99
BlueDriver Pro โ€” sensor only; $40.00 more than the Next-Gen on the same store ๐ŸŸข
$139.95
Autel AP200 โ€” dongle plus app; each extra listed brand $21.99 for a year in the App Store ๐ŸŸข
dongle not priced by Autel

One caution: BlueDriver's $99.95 is a discount from $119.95 and Autel's $99.99 is labelled a limited-time promotion, so both can move. All three are the maker's own figure on 30 September 2026, not a promise about next month.

Subscription or none: the exact terms, word for word

The answer is different for each of the four, so this section quotes each company rather than paraphrasing.

BlueDriver: none for the consumer sensor. The Pro product page carries three separate lines to that effect: a badge reading "Zero Subscription Fees or Add-ons", a comparison line reading "No subscriptions. No add-ons. Ever.", and the setup section's "No in app fees or add-ons." The App Store description repeats it as "No subscription required". What does need a connection is a short list in BlueDriver's own support article: repair reports, VIN decoding, maintenance schedules, recalls, service bulletins, sharing reports and downloading firmware updates require internet access, while reading and clearing codes, freeze frame, smog checks, Mode 6, MIL status and live data do not. That matters in a car park with no signal: the scan works, the report waits.

One BlueDriver product has a monthly fee: BlueDriver MAX, a business tool for dealers, auctions and fleets, from $99 a month plus a $199.95 device, minimum order of two. Its FAQ says "BlueDriver Max is not sold on an individual basis". If you see "BlueDriver subscription" anywhere, check whether the writer meant MAX.

FIXD: an optional paid plan, with the core features free. FIXD's FAQ table lists nine rows as included in the free app, among them "Read 7000+ engine codes in simple terms", "Clear check engine lights with one tap", "Monitor vehicle performance with live OBD2 data" and "Read ABS codes* (only available for select makes)". Six rows are Premium only, including repair cost estimates, the live Mechanic Hotline, "Predict future problems before they happen", the AI Mechanic chat, "Pass emissions the first time with Emissions Precheck" and unlimited used-vehicle history reports. The same FAQ prices Premium "for just $99.00 per year"; the App Store lists "Yearly FIXD Premium $99.99", "Monthly FIXD Premium $12.99" and "Weekly FIXD Premium $7.99"; the trial landing page sells a 14-day trial with a sensor for $19.99 and says that afterwards "you'll be charged $69.99" for a year. FIXD's returns page, stamped "Updated: 11/11/2021", allows a Premium refund within 30 days of the initial charge and says renewals are not refundable. The mechanics of those doors, and where each one is cancelled, are the whole subject of our FIXD page.

Autel AP200: free for generic OBD2 and one brand; paid per extra brand, per year. Autel's product page and the App Store listing both open with the same two lines: "All OBDII functions are available and free" and "One free vehicle's software with the initial purchase". The user manual sets the term on each: the included brand is "free and permanently valid", and "The purchased softwares are available for one year. You can renew them after expiration." The App Store listing then prices the extras by brand, ten of them shown: GM, Ford, Toyota, Honda, Nissan, Dodge, BMW, Jeep, VW and Benz, each "for one year $21.99". A household with a Toyota and a Ford that picks Toyota as its free brand therefore pays $21.99 a year for the Ford's brand software, while generic engine codes on the Ford stay free. Autel's pages do not say which of the 19 service functions each brand package carries; its BMS section, for example, says "This function is not supported by all vehicles."

One naming detail matters here. Autel also publishes lettered app versions, the AP200C, AP200H and AP200M, on a separate page, and for the H and M that page says "Download free software for your vehicle brand (Renew brand subscription after a year, additional brand lines available with in-app purchase)". On the plain AP200 the manual calls the included brand permanent, so check which version a listing names.

Autel AL619: no subscription stated. Neither the AL619 store page, its autel.com page nor its user manual mentions a subscription or a paid renewal. The page lists "Internet Updatable", and the manual says the tool must be registered at pro.autel.com before updating. Autel's general software-update page describes a "Total Care Program" for a full year of updates on its tools without naming which models it applies to; we found nothing on the AL619's own pages tying it to that program.

How much does each option cost if you keep it three years, and where does PulsCar land in that picture? For one car, BlueDriver is $99.95 or $139.95 once, and the AL619 is $99.99 once, as their own pages read today. FIXD is $59.99 if the free tier is enough; a buyer who adds Premium at the FAQ's $99.00 a year is at $356.99 after three years, before any trial-path discount. The AP200 adds nothing for one brand and $21.99 a year for each extra listed brand, so a second brand adds $65.97 over three years, on top of a dongle price Autel does not publish. PulsCar is not in that ladder at all: our free sound check is not a scanner, reads no codes and costs nothing, which is exactly why it cannot replace any of these four.

BlueDriver Pro Next-Gen or Pro โ€” "No subscription required"; internet only for reports, recalls, bulletins, firmware ๐ŸŸข
none
Autel AL619 โ€” no subscription on its page or in its manual; updates need tool registration ๐ŸŸข
none stated
Autel AP200 โ€” generic OBD2 and one brand free; each extra brand priced per year in the App Store ๐ŸŸข
$21.99 per brand per year
FIXD Premium โ€” optional; FAQ figure; App Store yearly is $99.99; trial door converts at $69.99 ๐ŸŸข
$99.00 a year in the FAQ
BlueDriver MAX โ€” business product, not sold on an individual basis, minimum order of two ๐ŸŸข
$99 a month plus device

Which codes each one reads: engine, enhanced, ABS, airbag, TPMS

"Reads codes" is on every product page here, and it hides the most important difference between these tools. Every OBD II scanner reads the generic engine and emissions codes that turn on the check engine light, because U.S. rules require 1996 and newer gasoline cars to carry OBD II, and BlueDriver's support page says those generic codes are readable on any OBD II vehicle. The California Air Resources Board's fact sheet states the rule: "All 1996 and newer model year gasoline and alternate fuel passenger cars and trucks are required to have OBD II systems", and it adds that the U.S. EPA requires 1996 and newer passenger cars and trucks sold in any state to meet federal OBD requirements. The difference between scanners starts where that rule ends: codes stored in the brake, airbag, tyre-pressure, transmission and body modules are not standardised, and each maker has to support them make by make.

BlueDriver's own support article explains the split better than most reviews do. Generic codes "generally cover the engine and emissions equipment" and "will be readable on any OBDII compatible vehicle"; enhanced codes "are different for every manufacturer and are not accessible using generic scan tools". With that in mind, here is what each maker claims.

BlueDriver. The product page lists "Advanced Diagnostics (ABS, Airbag, SRS, and TPMS) Available On:" thirteen make groups: GM, Ford, Chrysler, Toyota, Nissan, Mazda, Subaru sold in the US, Mitsubishi from 2008, Hyundai and Kia from 2011 (the App Store says 2012), Mercedes and Smart from 2005, BMW and Mini sold in North America from 2005, Honda and Acura sold in North America from 2003, and Volkswagen group sold in North America. Transmission appears on the product page's feature list and in the checker, and the App Store description says the app reads "check engine, ABS, airbag, transmission, and more". The page closes with a caveat: where enhanced diagnostics are not yet offered on a vehicle, "all other BlueDriver features, including trouble code lookup and Repair Reports work on ANY vehicle with an OBD2 port."

FIXD. The FAQ lists makes for "standard codes" and a longer list for ABS, from Acura through Volvo, with "Partial Coverage for" Hummer and Renault. On the pages we read, FIXD makes no claim to read airbag, TPMS or transmission module codes, and so this page does not say it does. Its free-tier line on ABS carries its own qualifier, "only available for select makes", and FIXD deserves credit for printing the list.

Autel AP200. Autel describes the AP200 as a tool for "diagnostic functions of all systems", with up to 19 service functions, and the brand software you install is what goes beyond generic OBD II. Autel's own AP200 page, manual and app-store listings do not name ABS, airbag or transmission, so this page does not credit it with them by name. On brands you have not installed, the generic OBD II functions work free. The lettered AP200H is narrower by design, scanning "4 main systems (Engine, Transmission, SRS, and ABS systems)".

Autel AL619. The handheld reads generic codes and manufacturer-specific engine codes, and its headline feature is ABS and SRS: the page says it "Turns off Check Engine Light (MIL) and ABS/SRS warning lights". The manual says the ABS and airbag functions cover "more than 50 US, Asian and European vehicles" and prints a list of makes from Acura to Abarth, noting that eight European makes are only on the EU version; the store page's general coverage line says "more than 80". It does not list TPMS, and the manual names the transmission control module only as a module you can select for generic OBD II data, not as an enhanced system of its own.

Generic engine and emissions codes โ€” the codes behind the check engine light; each maker states its own year and fuel limits ๐ŸŸข
All four
ABS codes โ€” BlueDriver on its listed makes; FIXD free on its listed makes; AP200 not named, "all systems" on the installed brand; AL619 on its listed makes ๐ŸŸข
Named by three, make-dependent
Airbag (SRS) codes โ€” named by BlueDriver and the AL619; not named on the AP200's or FIXD's pages ๐ŸŸข
BlueDriver, AL619
TPMS โ€” BlueDriver lists TPMS codes on its make groups; the AP200 lists TPMS as a service function ๐ŸŸข
BlueDriver codes; AP200 service
Transmission module codes โ€” named by BlueDriver; among Autel's handhelds, by the ML629; the AL619 lists no transmission diagnostics beyond generic OBD II ๐ŸŸข
BlueDriver

The practical reading: if the light on your dashboard is the airbag warning, FIXD's pages list no airbag coverage (its ABS list covers brake-system codes on listed makes), BlueDriver and the AL619 name airbag coverage on their make lists, and the AP200 claims "all systems" on the brand you install without naming airbag; Autel's separate AP200C and AP200H pages do name ABS and SRS.

Live data, freeze frame, Mode 6 and readiness

These four features separate "tells me the code" from "helps me work out what happened", and some makers list them on the box while others keep them in a manual.

Live data is the stream of sensor values while the engine runs. All four claim it. FIXD's FAQ names examples, "engine coolant temperature, control module voltage, engine runtime, EVAP system pressure, fuel trim, and oxygen sensor voltage", and puts live data in the free tier in its FAQ table, although its Premium trial page also lists "Live data" among what the trial includes. BlueDriver's App Store listing describes "live data with multi-PID interactive graphing". The AP200 manual describes live data as "real time PID data from ECU", and the AL619 page says it "Reads, stores and plays back live PCM data stream and live sensor data" and graphs it.

Freeze frame is the snapshot of sensor values the car stored at the moment a code set, and it is often more useful than the code itself: it tells you whether the fault happened cold or hot, at idle or at speed. BlueDriver lists it on the product page; the AP200 manual puts it in its "DTC & FFD" menu; the AL619 manual gives it its own section. On the FIXD pages we read, freeze frame is not listed among the features, so we make no claim either way.

Mode 6 is the car's own record of self-test results for monitored systems, including misfire counts. BlueDriver names it Mode 6 and describes it as "manufacturer specific self tests (includes misfires for 2008+ model vehicles)". The AP200 manual has an "On-Board Monitor" option showing on-board monitor test results, and the AL619 manual an "On-Board Monitor Test" and lists Mode $06 among its OBD II modes; neither AP200 document uses the name Mode 6. FIXD's pages do not mention Mode 6.

Readiness is the one that matters most to anyone buying a used car or facing an emissions test. When codes are cleared or a battery is disconnected, the car's monitors reset to "not complete" and have to be re-run by driving. CARB's fact sheet explains the consequence plainly: "If too many readiness indicators are "incomplete," the vehicle will fail the inspection". BlueDriver's "Smog Check" feature reads these monitors and its support article on used cars says that if several are listed as not complete, "this may be an indication that codes have recently been cleared". The AP200 has "I/M Readiness" with two views, since codes were cleared and this drive cycle; the AL619 manual gives it a section. FIXD's nearest feature is "Emissions Precheck", which its trial page calls an "easy at-home test exclusive to FIXD Premium"; its pages do not say it shows readiness monitors.

Live data โ€” free in FIXD's table; included in BlueDriver, AP200 and AL619 ๐ŸŸข
All four
Freeze frame โ€” listed by BlueDriver, AP200 and AL619; not listed on FIXD's pages ๐ŸŸข
Three of four listed
Mode 6 / on-board monitor tests โ€” BlueDriver names Mode 6; AP200 and AL619 list on-board monitor tests; not on FIXD's pages ๐ŸŸข
Three of four listed
Readiness monitors (smog check) โ€” included in BlueDriver, AP200 and AL619 ๐ŸŸข
Included
FIXD Emissions Precheck โ€” an at-home emissions test, in FIXD Premium; readiness monitors not named ๐ŸŸข
Premium only

BlueDriver adds one feature the others do not describe in the same terms, and it is worth knowing about if you are looking at a used car: "MIL Status", which, where the car supports it, reports the distance driven, engine run time and number of warm-ups since codes were last cleared. A light cleared yesterday is easier to spot. The AP200 manual lists a "Vehicle Status" screen that shows the state of the Malfunction Indicator Light, and the AL619 manual has vehicle information and modules-present screens; neither manual describes the since-cleared counters in the same terms.

Before you clear any light. Write down the code and freeze frame first: the AP200 manual says clearing erases "DTCs, freeze frame data and manufacturer specific enhanced data", and the AL619 manual adds that readiness status for every monitor is reset to not ready or not complete. CARB warns that a blinking check engine light "indicates that a malfunction is occurring that could be damaging your catalytic converter". An airbag or brake warning is a safety system reporting a fault; get it inspected rather than just cleared.

"Repair report" means three different things

All three makers use the words "repair report" or something close to it, and they are not describing the same thing. This is the easiest place on the page to buy the wrong product by reading a feature list quickly.

At BlueDriver, a repair report is advice about the fix. The product page says that for each code the app will "generate a report for your vehicle containing possible causes, reported fixes, and more", and the compatibility page describes those fixes as "reported by our SAE certified technicians", alongside BlueDriver's "Fear No Fix" how-to videos. The App Store listing adds that you can "preview a Repair Report without a Sensor by entering your VIN and a trouble code", which is a free way to see what the feature looks like before you buy anything. Reports need an internet connection, and they are included in the one-time price.

At FIXD, the equivalent is paid. The free app gives you, per its features page, "the severity o f the problem, the consequences of continuing to drive with that problem, and a 2-3 sentence definition" of each code. The most likely repair and its cost are Premium: the FAQ says "With FIXD Premium you'll also know the most likely repairs and their costs." FIXD adds a "live Mechanic Hotline", also in Premium; we found nothing equivalent listed on the BlueDriver or Autel pages we read. One FIXD page reads differently: its Premium trial page lists "Get accurate cost estimates for your vehicle for any common repairs" among features it calls free with the sensor, while the FAQ table and fixd.com put cost estimates in Premium; we show both lines.

At Autel, a repair report is a record of the scan. The AP200 page promises to "Generate repair reports of tested vehicles and support PDF format for easy sharing and printing"; the manual describes the report as a saved record of a diagnostic session. That is useful, for handing a mechanic or a seller a dated scan, but it is not a list of likely fixes. The AL619's nearest feature is different again: "Troubleshooter code tips", built into the handheld, and printing via a Windows PC.

None is better in the abstract. For walking into a shop knowing the likely fix, BlueDriver's report or FIXD Premium; for a dated, shareable record of a scan, Autel's PDF or BlueDriver's share function. Just do not assume the words mean the same thing.

Service functions and bidirectional control

A code reader listens. A bidirectional tool also talks back: it commands the car to run a test, switch a component or reset a system. This is where the four differ most, and where the Autel app lists by far the most functions.

Autel AP200. The page lists "Support up to 19 specific functions, including Oil Reset, EPB, BMS, SAS, DPF, TPMS, IMMO, etc.", and the Google Play description expands the list to brake bleed, injector, suspension, throttle and seats. The manual's Component Test section says it "enables bi-directional control of the ECM so that the diagnostic tool is able to transmit control commands to operate the vehicle systems", and it adds a note in the same OBD II menu: "Some functions are supported only on certain vehicle makes." Autel's pages do not say which service functions come with the free brand and which with a paid one, so check the function for your make before buying.

BlueDriver. BlueDriver's pages do not use the word bidirectional; its compatibility checker separates two kinds of service. It lists "Active Service", described as "Communicate with your vehicle to perform service tasks", with Battery Registration as the example, and separately "Passive Service", described as "Get steps to perform the service tasks yourself", with oil light and TPMS light resets done through the car's own menus. The checker shows which of these apply to the car you enter.

Autel AL619. Its Component Test is narrow: the manual describes it as starting an evaporative-system leak test, and "The scan tool itself does not perform the leak test, but commands the vehicle's on-board computer to start the test." No other service functions are listed.

FIXD. FIXD's pages list no service functions or bidirectional tests. Its maintenance feature is a schedule and reminders, "mileage-based reminders to alert you when you are approaching a maintenance interval", which is a different and genuinely useful thing, but it does not send commands to the car.

One caution applies to all four and to every scan tool. Service functions change what the car does, and a wrong step on the wrong vehicle can cause trouble. BlueDriver's support centre makes the point in a Honda VSA calibration article about a manual jumper-wire procedure, not a scan-tool function: "Do not attempt a VSA calibration yourself unless you understand all steps and are familiar with the OBDII port and vehicle." The same caution fits any service function, from any maker.

Phone or handheld, iPhone or Android

Three of the four are a plug plus a phone app; one is a handheld with its own screen. A phone-based tool is only as current as its app.

BlueDriver supports both platforms. Its support article says "All iOS devices running iOS 13 or higher are fully compatible" and "All Android devices running Android 8.0 or higher are fully compatible". The App Store listing we read the same day says "Requires iOS 16.6 or later." The support article is dated 14 May 2026; trust the store listing, because your iPhone enforces it. On Android, BlueDriver's setup steps ask for location permission, "needed for stable Bluetooth pairing". The iPhone app was last updated on 8 September 2026, version 8.12.2, and the Android app shows "Updated on Sep 10, 2026".

FIXD is on both stores. Its App Store listing requires iOS 18.0 or later, the newest requirement of the three apps, and shows version 26.29 released on 26 September 2026; the Google Play listing shows "Updated on Sep 28, 2026". FIXD's features page describes the sensor as connecting "via Bluetooth Low Energy".

Autel AP200 is on both stores too, with differences worth reading. The App Store listing is marked "Only for iPhone" and "Requires iOS 12.0 or later", and its version history shows version 1.47 of 5 September 2023 as the latest, with no later iOS version listed. The Google Play listing, titled "Autel MaxiAP200", shows "Updated on Mar 31, 2025". The manual also explains a quirk: on iOS, a purchased brand package appears in the list, and tapping it opens "another application for diagnosing", and Autel publishes separate package apps such as Diag-USA alongside the main one.

Autel AL619 needs no phone at all. It runs from the car's battery, 8.0 to 18.0 V through the cable, has a 320 by 240 colour screen, and weighs 280 g without its cable. Updates go through Autel's Maxi PC Suite, which the manual says runs on Mac and Windows: after registering the tool, you move its TF card to a card reader and update from the computer. Printing needs a Windows PC. It is the only one of the four that scans with no app or phone; registration is needed only to update (and, per Autel's warranty page, dates the warranty if you have no receipt).

BlueDriver โ€” iPhone and iPad; Android 8.0 or higher per its support page ๐ŸŸข
iOS 16.6+ in App Store
FIXD โ€” iPhone and Android; App Store version dated 26 September 2026 ๐ŸŸข
iOS 18.0+ in App Store
Autel AP200 โ€” iPhone only on iOS; last iOS version dated 09/05/2023; Android updated Mar 31, 2025 ๐ŸŸข
iOS 12.0+ in App Store
Autel AL619 โ€” handheld; own screen; powered by the car; updates via PC software ๐ŸŸข
no phone needed

Accounts are part of this too. BlueDriver's setup text still lists creating an account or logging in as a step, while a 2026 App Store release note (version 8.7) says "Creating an account is no longer required to use BlueDriver." FIXD's setup asks you to create an account, and the AP200 manual requires an Autel ID bound to the dongle before buying brand software. The AL619 needs a registration only to update, so it is the one route with no account or phone needed to scan.

Vehicle coverage checkers: test before you buy

Each maker publishes some limit on which cars work, a year rule or a "not compatible with all vehicles" note, and each offers a way to check. Using that check is the single most valuable five minutes in the buying process, because coverage of the systems you care about (ABS, airbag, TPMS) is make-, year- and market-specific.

BlueDriver has the more detailed of the two checkers we read, with separate pages for the Pro and the Pro Next-Gen. It asks first where the car was sold new, and explains why: "OBDII compatibility depends on the region or country in which a vehicle was originally sold (not where it was assembled)." After year, make, model and engine, it lists which systems the tool can read and clear on that car, from Engine through ABS and brakes, transmission, airbags, TPMS, four-wheel drive and hybrid systems, and which features apply. Its page also carries a note for vehicles where "the exact systems that are supported are currently unknown", which is an honest thing for a checker to say.

FIXD puts a checker on its homepage under "DOES FIXD WORK ON MY CAR?", with year, make and fuel type (gas, hybrid, diesel, electric). The rule printed above it is "FIXD works with all gas-powered cars and trucks built after 1996 and diesels built after 2008." The features page adds a footnote for other markets: "Also compatible with cars 2006 and newer that are sold outside the U.S." On the day we read it, the year menu on fixdapp.com's homepage ran from 1996 to 2024; the ABS list is in the FAQ.

Autel runs a vehicle coverage search on autel.com by product model and function; we did not run it for this page. The AL619 store page suggests the direct route: "AL619 is not compatible with all vehicles, please contact us for a check before placing an order." The AP200 manual describes the app as "almost compatible with all vehicle models of European, Asian, and North America makes".

BlueDriver compatibility checker โ€” country of first sale, year, make, model, engine; system-by-system result ๐ŸŸข
system-by-system result
FIXD homepage checker โ€” year, make, fuel type; ABS make list in the FAQ ๐ŸŸข
year, make, fuel type
Autel vehicle coverage search โ€” by product model and function; not run for this page ๐ŸŸข
by product and function

Small inconsistencies inside the makers' own pages show why the checker beats the brochure. BlueDriver's product page dates its Hyundai and Kia enhanced coverage "(2011 models & newer)", while its App Store description says "Hyundai/Kia (2012+)"; and the same product page's list reads "Chrysler Including Ford, Lincoln, & Mercury.", which repeats the Ford line. FIXD's homepage says "built after 1996" while its features page says "1996* and newer". Autel's AL619 page says in one paragraph that it reads codes on "all post 1996 domestic, post 2006 European and post 2009 Asian vehicles" and in another that it is "Compatible with domestic, Asian and European vehicles, 1996 and newer". If your car sits near one of those year lines, the checker, or an email to the maker with your VIN, is the only answer that counts.

Warranty and returns, side by side

A scan tool that does not talk to your car is only a problem if you cannot send it back. The return windows here differ by a factor of six, and each depends on where you bought.

BlueDriver offers the longest window by far. Its refund policy is headed "180-Day Money-Back Guarantee" and applies "on products purchased directly from BlueDriver through its official sales channels". A return request must reach support "within 180 days of confirmed delivery", a return authorization is required first, and the refund is issued after the product is received and inspected; processing "may take 5โ€“10 business days after approval". Bought from a retailer or marketplace instead, "the return and refund policy of that seller will apply". The footer adds a one-year limited warranty and free shipping. The policy also asks customers to contact support before any chargeback and says a chargeback before completing the return process may void the guarantee.

FIXD gives 30 days: "request a full refund within 30 days after the date of delivery", with a return authorization requested inside that window, and the product "must be purchased from FIXD Automotive or from an approved affiliate/re-seller." Its page notes that "Shipping fees, warranty, taxes, and customs fees are non-refundable." The one-year limited warranty is a replacement warranty: "The product will be replaced with a new product. No refunds will be given under the warranty." Subscription refunds follow separate rules, covered on our FIXD page.

Autel's store also gives 30 days: "You have 30 calendar days to return an item from the date you received it." The item must come back in its original packaging with all accessories, a return has to be requested before shipping anything, and on a change-of-mind return "the customer will be responsible for the return shipping costs". The warranty page gives one year, repair or replacement at Autel's option with proof of purchase, and adds a useful line for anyone who lost the receipt: "In lieu of proof of purchase, tool or tablet is warranted one year from tool/tablet registration." The AP200 manual carries Autel's own limited one-year warranty. Because the AP200 is not listed on Autel's store, we found no Autel return terms for it; ask the seller.

BlueDriver, bought direct โ€” money-back guarantee from confirmed delivery; authorization first; one-year limited warranty ๐ŸŸข
180 days
FIXD sensor, bought direct โ€” full refund from delivery; shipping and taxes non-refundable; one-year replacement warranty ๐ŸŸข
30 days
Autel AL619, bought on store.autel.com โ€” original packaging; buyer pays return shipping on change of mind; one-year warranty ๐ŸŸข
30 days
Autel AP200 โ€” not listed on Autel's store; the selling retailer's terms apply; Autel's one-year limited warranty per the manual ๐ŸŸข
seller's policy

App ratings, with counts and dates

Star ratings are the least precise evidence here. Each figure is what the store displayed on 30 September 2026, except the AP200 Google Play rating, re-read on 8 October 2026, with its count; they are platform aggregates, marked โšช.

BlueDriver, App Store โ€” Apple's public lookup data gives 13,724 ratings; version 8.12.2 of 8 September 2026 โšช
4.6 ยท 14K ratings
BlueDriver, Google Play โ€” 1M+ downloads; updated Sep 10, 2026 โšช
3.5 ยท 17.2K reviews
FIXD, App Store โ€” Apple's public lookup data gives 25,818 ratings; version 26.29 of 26 September 2026 โšช
4.6 ยท 26K ratings
FIXD, Google Play โ€” 1M+ downloads; updated Sep 28, 2026; "#1 top grossing auto & vehicles" badge โšช
4.1 ยท 30.1K reviews
Autel MaxiAP-AP200, App Store โ€” iPhone only; latest version 1.47, dated 09/05/2023 โšช
2.2 ยท 167 ratings
Autel MaxiAP200, Google Play โ€” 100K+ downloads; updated Mar 31, 2025; rating re-read 8 Oct 2026 โšช
4.3 ยท 2.72K reviews
Autel AL619 โ€” a handheld with no app, so no store rating exists to compare โšช
no app

Three readings. BlueDriver's two stores disagree by more than a full star, 4.6 on Apple and 3.5 on Google Play, on counts of the same order; we did not read enough reviews to say why. FIXD's app ratings are 4.6 and 4.1; how its subscription works and what its review profiles show is set out on our FIXD page. The AP200's iPhone rating is low and its Android rating is not, and both rest on far smaller counts; a rating tells you how app users felt, not what the dongle reads once connected. Google Play also shows a phone-only figure for each app; we quote the headline.

Three traps a careful buyer still walks into

Trap one: comparing the plug and not the years after it. The situation: a buyer lines up $59.99, $99.95 and $99.99 and picks the lowest number. What is real: two of the four have terms that continue after the day of purchase. FIXD's repair cost estimates, emissions precheck and Mechanic Hotline are Premium, $99.00 a year in its FAQ; each of the ten brands the AP200's App Store listing shows is $21.99 for one year. BlueDriver states no subscription; the AL619's pages list no ongoing charge, though Autel's software-update page describes a yearly program for its tools without naming models. The price: a cheaper plug that ends up the dearer tool by year three, or a feature you assumed was included turning out to be paid. The defense: decide which rows of the tables above you actually need, then price three years, not one.

Trap two: buying through a marketplace and expecting the maker's return window. The situation: a buyer reads "180-day money-back guarantee", orders a BlueDriver from a general marketplace because it arrives a day sooner, and finds in month two that the sensor will not read the airbag module on their car. What is real: BlueDriver's policy covers "orders where BlueDriver or one of its affiliated entities is the seller of record"; elsewhere, the seller's own policy applies. FIXD's 30 days cover purchases from FIXD or an approved affiliate or reseller, Autel's 30 days are its own store's terms, and the AP200 is not listed on Autel's store at all. The price: a tool you cannot return, for a car it does not fully read. The defense: run the maker's checker first, then buy from the maker if the return window is part of why you chose the brand.

Trap three: reading a feature word as if it meant the same thing everywhere. The situation: a buyer sees "repair reports", "all systems" and "ABS" on three product pages and assumes the same thing is on offer in each. What is real: BlueDriver's repair report suggests fixes; Autel's is a PDF record of a scan. Autel's "all systems" is its description of the AP200 and names no specific module. "ABS" at FIXD is "only available for select makes", and FIXD's feature, FAQ and trial pages list no airbag coverage. The price: the right brand for someone else's car. The defense: read the fine print under each feature and the checker result for your exact vehicle; the tables on this page are built to make that quick.

Three composite situations, decoded

These are composite scenarios, not individual customers. They are written in the subjunctive on purpose, built only from facts already on this page, and they contain no invented names, prices or dates.

Scenario 1: the airbag light, not the check engine light. Suppose a driver's airbag warning light comes on in a Honda first sold in North America, and the check engine light stays off. A generic code reader would find nothing, because the fault is stored in the airbag module, not the engine computer. BlueDriver's product page lists airbag and SRS diagnostics for Honda and Acura sold in North America from 2003; the AL619 manual lists Honda among its ABS and airbag makes; the AP200's pages promise "all systems" on an installed Honda package without naming airbag, so ask Autel before relying on it; FIXD's feature and FAQ pages list no airbag coverage. Lesson: the warning light decides the shortlist before price does.

Scenario 2: two brands in one driveway and a parking-brake job. Suppose a household runs a Ford and a Toyota and wants a scan tool's electronic parking brake (EPB) function for a brake job at home. The AP200 lists EPB among its service functions; Autel's pages do not say whether the free brand includes it, and the App Store lists each extra brand at $21.99 for one year. BlueDriver's checker lists battery registration as an active service on supported cars but lists no parking-brake service function, only reading codes from parking brake systems as equipped. Lesson: for service work, the AP200 is the one that lists EPB, but confirm the function for your make first; whether it is cheapest depends on a dongle price Autel does not publish.

Scenario 3: the used car with a suspiciously clean scan. Suppose a buyer plugs a scanner into a used car at a lot, sees no codes and is about to relax. BlueDriver's own support article names the next move: if several readiness monitors read not complete, "this may be an indication that codes have recently been cleared", and its MIL Status screen can, where the car supports it, show distance and engine time since the clear. The AP200 and AL619 read the same monitors; FIXD's nearest feature, Emissions Precheck, is Premium. Lesson: on a used car, readiness is the check that matters, and a clean code list is the start of the inspection, not the end. The full checklist lives on our used-car checklist, and what a shop inspection costs is on the inspection-cost page.

What none of the four can see

Every product on this page reads what the car's computers have stored: the right tools for a warning light, the wrong tools for faults that never set a code. The California Air Resources Board describes the design in one line: the system is built to "monitor virtually every component that can affect emission performance". A worn wheel bearing, a bushing or a loose heat shield is not something the fact sheet describes these systems as watching. FIXD, to its credit, acknowledges the gap in its own table: its free app lists "Diagnose issues FIXD can't detect with Manual Diagnostic", and its trial page offers that tool "to find out what's causing those funny noises under the hood". It is a feature of the app, not a reading from the car.

We measured how often this matters for the FIXD page. In 39,355 complaints to the National Highway Traffic Safety Administration about ten high-volume nameplates, model years 2015 to 2022, 3,838 complaints described a sound and mentioned no light, no code and no scan: 79% of every complaint in that sample that described a sound. The method and limits are on that page; these are mentions, not measured events. The point for a scanner buyer is narrow: if your problem is a noise and the dashboard is quiet, a clean scan from BlueDriver, Autel or FIXD is the expected result, not an all-clear.

Where a free sound check fits, and where it does not

Full disclosure again: this is our side of the page. PulsCar's sound check asks you to film your engine running for 30 seconds, and a report arrives by email in about ten minutes. The homepage terms are "No payment, no card, no subscription." If a clip cannot support a confident verdict, the report says "inconclusive" rather than guessing.

It does none of what this page compares: no trouble codes, no clearing, no live data, freeze frame or readiness, no service functions, and nothing to plug in. It is engine-framed, so a brake squeal or a suspension clunk sits largely outside it. For a warning light, buy one of the scanners above.

Should you use one of these scanners or PulsCar's free sound check for the problem you have right now? The rule fits in one line: a warning light that comes with a stored code needs a scanner; a new noise with no light is acoustic and needs a microphone. If the check engine, ABS or airbag light is on, one of these scanners is the right purchase, and the tables above tell you which. If there is a knock, rattle or whine from the engine and the dashboard is quiet, none of the four will name it, because there is nothing stored to read, and the free check costs nothing to try first: 30 seconds of the engine running, no card, report by email. If you have both, do both. A brake, wheel or suspension noise, a smell, a leak or a pull needs a physical inspection.

Scanner says no codes but the car still sounds wrong?
Try the free sound check โ€” 30 seconds, about 10 minutes

Record 30 seconds of your engine running on any phone. PulsCar's AI listens for the acoustic signature and sends back the likely cause, a severity assessment and a repair-cost range, for the sounds that come with no warning light and no stored code. It does not judge whether the car is safe to drive. The report arrives by email, so use the address you actually read. Free, no card, no subscription.

๐Ÿ” Try Sound Diagnosis โ€” Free

What we looked for and did not find

Naming the gaps is part of the method. Each item below was an actual search on 30 September 2026.

No Autel-published US price for the AP200. It is not listed on store.autel.com, and Autel's product page carries no price. The Amazon page that carries Autel's name showed "No featured offers available" when we opened it. We quote no figure rather than borrow one from a reseller.

No FIXD statement on freeze frame, Mode 6, airbag, TPMS or transmission codes. We read the FAQ, features page, homepage and trial page. Absence of a claim is not proof of absence of a feature, so the tables say "not listed", and nothing stronger.

No update-fee terms for the AL619. The page says "Internet Updatable" and the manual describes registration and updating; neither names a price or a term. We checked Autel's software-update page, which describes a yearly program for its tools without listing models.

No independent accuracy test. Nobody we could find outside the makers publishes a controlled test of which codes each tool reads on which cars, and we did not run one. The makers' checkers are the best evidence available, and we say so rather than invent a benchmark.

No review-site verdicts. We did not use review sites as sources for any fact. We did not read Trustpilot or BBB profiles for BlueDriver or Autel for this page; FIXD's are on our FIXD page.

The EPA's OBD page at the address we used returned a not-found error. We relied on the California Air Resources Board's fact sheet, which states both the California and federal rules.

Your plan: before you order, on the day, and the first week

Before you order (ten minutes, free):

  1. Name the light. Check engine only: any of the four. ABS: BlueDriver, FIXD and the AL619 on their listed makes; for the plain AP200, ask Autel first. Airbag: BlueDriver or the AL619 on their listed makes; for the plain AP200, ask Autel first. No light but a noise: none of them; start with the free sound check.
  2. Run the maker's checker for your exact year, make, model and, for BlueDriver, the country where the car was first sold. For Autel, use its coverage search or email the maker with your VIN.
  3. Decide whether you want a phone app or a handheld, and check the app's current minimum iOS version in the App Store, not in a support article.
  4. Price three years, not one: add FIXD Premium if you want its estimates or Emissions Precheck, and $21.99 a year per extra brand on the AP200 as the App Store lists it.

On the day you order: 5. Buy from the maker if the return window matters: 180 days at BlueDriver, 30 at FIXD and at Autel's store, each tied to where you bought. 6. Screenshot the product page, price and return line. Prices on two of these pages show a struck-through or "Limited Sale" price. 7. On an AP200, check whether the page says AP200, AP200C, AP200H or AP200M: the plain AP200's free brand is permanent by its manual; the lettered versions speak of renewing a brand or system subscription after a year.

In the first week: 8. Scan every car you intend to use it on while you can still return it, and check that the systems you bought it for (ABS, airbag, TPMS) actually respond. 9. If you are shopping for a used car, practise the readiness check on your own car first so you recognise normal. 10. If a light comes back after a repair, read the freeze frame before clearing anything; it records the conditions when the code set.

For the neighbours of this page: the ranked OBD2 scanner shelf, the full diagnostic-app comparison, the OBDLink MX+ review, which kind of diagnostic tool your problem needs, what AutoZone's free scan gives you, sound AI versus OBD scanners, what a check engine light means, and what a diagnostic should cost.

Sources and documents

Every number and quotation above comes from one of these pages, each opened and read on 30 September 2026 unless marked otherwise.

  1. BlueDriver Pro product page โ€” price, no-subscription lines, enhanced make list: us.bluedriver.com/products/bluedriver-scan-tool
  2. BlueDriver Pro Next-Gen product page โ€” $99.95 from $119.95, "the ideal OBDII scanner for newer North American model vehicles": us.bluedriver.com/products/bluedriver-pro-scan-tool-next-gen
  3. BlueDriver compatibility checkers: Pro checker, Next-Gen checker
  4. BlueDriver refund policy โ€” the 180-day money-back guarantee and its conditions: us.bluedriver.com/policies/refund-policy
  5. BlueDriver support articles: phone or tablet, internet connection, code types, codes cleared recently, Honda VSA calibration
  6. BlueDriver MAX โ€” the business product, its monthly price, minimum order and FAQ: bluedrivermax.com
  7. FIXD FAQ โ€” prices, the free-versus-Premium table, make lists, live data: fixdapp.com/faq
  8. FIXD homepage and features page โ€” hero price, compatibility checker and rule: fixdapp.com, fixdapp.com/features
  9. FIXD Returns and Warranty: fixdapp.com/returns-warranty
  10. FIXD Premium trial page and fixd.com order page โ€” $19.99 trial, "you'll be charged $69.99", $59.99 with the household limit: trial page, fixd.com
  11. Autel MaxiAP AP200 product page: autel.com/mk1/3262.jhtml
  12. Autel MaxiAP AP200 user manual: MaxiAP AP200 User Manual (PDF); quick start guide: PDF
  13. Autel MaxiAP AP200C/H/M page โ€” the lettered versions and their renewal wording: autel.com/mk1/3533.jhtml
  14. Autel AutoLink AL619, store page and autel.com page: store page, autel.com page
  15. Autel AutoLink AL619 user manual: AL619 User Manual (PDF)
  16. Autel store neighbours used for model choice โ€” AL519 at $59.99, ML629 at $126.88, MD906 Pro at $299, MK808BT Pro at $549: AL519, ML629, MD906 Pro, MK808BT Pro
  17. Autel store return and warranty pages: returns, warranty
  18. Autel vehicle coverage search and software-update page: vehicle coverage, software updates
  19. Apple App Store listings: BlueDriver, FIXD, MaxiAP-AP200, Diag-USA; exact rating counts from Apple's public lookup
  20. Google Play listings: BlueDriver, FIXD, Autel MaxiAP200
  21. Amazon page carrying Autel's name for the AP200 โ€” read only to confirm "No featured offers available"; no other fact taken from it: amazon.com AP200 listing
  22. California Air Resources Board, OBD II Systems Fact Sheet: OBD II fact sheet
  23. U.S. EPA: the EPA OBD page at the address we tried returned a not-found error and is not quoted; the EPA's inspection and maintenance page was read for context only
  24. PulsCar's NHTSA complaint count (39,355 complaints, computed 6 September 2026, method and limits), published on FIXD vs PulsCar
  25. PulsCar homepage โ€” the free sound check terms: pulscar.io

How this page was built: every product fact was read on 30 September 2026 from the maker's own properties (us.bluedriver.com, support.bluedriver.com and bluedrivermax.com for BlueDriver; fixdapp.com and fixd.com for FIXD; autel.com, store.autel.com and Autel's published manuals for Autel), plus the Apple App Store, Apple's public lookup data and Google Play, and quoted as published. Where two of a maker's own pages disagree, both are shown. Star ratings and review counts are the platforms' figures, marked โšช. No hardware was tested and no head-to-head bench test was run; which systems a tool reads on a particular car is answered only by the maker's checker or the maker itself. The NHTSA complaint count is PulsCar's own, computed and documented on the FIXD page. The three scenarios are composite and contain no invented names, amounts or dates. PulsCar sells none of the products compared here.

Prices verified: 30 September 2026 ยท Technical documents verified: 30 September 2026 ยท Reviewed quarterly

Bought one of these and found your car read differently from what the maker's checker promised, better or worse? Email [email protected] with the tool, the car's year, make and model, and what it did or did not read. A documented counter-example changes this page faster than anything we could write.