Website Review
What is Memtest86+?
Memtest86+ is a free, open-source, stand-alone memory tester for 32-bit and 64-bit x86 computers (and some LoongArch64 systems), distributed under the GNU GPL v2.0. It boots directly from removable media — independent of Windows, Linux or macOS — and runs its own set of test algorithms against your RAM, which the page describes as more thorough than the memory check built into a typical BIOS or UEFI.
It is not the same product as Memtest86, which the page notes has been closed-source freemium software owned by PassMark since 2013. The two share a name history, not a codebase.
What it is actually for
- Diagnosing instability. If a PC crashes, freezes or throws blue screens, the page treats RAM as one of the most common causes and testing it as the first thing to try.
- Validating new or overclocked hardware. Before putting a new PC or server into production, or after overclocking CPU or RAM, a clean run gives you a baseline that no memory faults are present.
- Confirming a suspected faulty module. A failing result points at RAM rather than the operating system, drivers or storage.
What using it involves
You write the image to a USB flash drive — the Windows USB Installer on Windows, dd or a similar raw-write utility on Linux, and a burner such as balenaEtcher on macOS — then reboot and pick the drive from the boot menu. It runs outside any operating system, so a machine that will not boot an OS can still be tested.
The practical trade-off is time and interpretation. A thorough pass takes hours on a large machine, and the tool reports pass/fail and error addresses rather than telling you which stick to replace. On a multi-module system you may need to re-test modules individually to isolate the culprit.
Next step
If you are chasing intermittent crashes, run it overnight before replacing anything: a clean result redirects you toward drivers, storage or power, while errors give you a concrete reason to reseat or swap modules. Start at Memtest86+.
Choosing between the two tools
| Memtest86+ | Memtest86 (PassMark) | |
|---|---|---|
| Licensing | Open source, GPL v2.0 | Closed-source freemium |
| Cost | Free | Free tier plus paid editions |
| Boot modes | BIOS legacy, UEFI, or via a Linux-protocol bootloader | Not described here |
If licence terms or auditability matter — for example in a managed fleet — the open-source option is the simpler fit. If you want vendor support and a polished commercial interface, the freemium tool is the alternative.
How do I create a bootable Memtest86+ USB drive on Windows, Linux, or macOS?
Memtest86+ is distributed as a bootable image, so the job is to write that image to a USB stick in raw form and then boot the machine from it. The method differs slightly by operating system, but the outcome is the same.
Windows
Download and launch the Windows USB Installer, plug in a standard FAT32-formatted USB drive, and follow its prompts. Reboot and select the USB drive from your boot menu. This is the simplest route because the installer handles the image writing for you.
Linux
Write the ISO image directly to the raw device. The dd command works, or use a utility that does the same job, such as balenaEtcher. Point it at the whole disk (for example /dev/sdX), not a partition (for example /dev/sdX1).
macOS
balenaEtcher is the recommended way to burn the image to a USB flash drive. As on Linux, the image must go to the raw device rather than a mounted volume.
| Platform | Recommended method | Key caution |
|---|---|---|
| Windows | Windows USB Installer | Use a FAT32-formatted drive |
| Linux | dd or balenaEtcher |
Write to the raw device, not a partition |
| macOS | balenaEtcher | Unmount the volume before writing |
Practical notes
- Writing the image erases everything on the USB drive, so use one you can spare.
- On x86 systems, Memtest86+ can boot directly via BIOS (legacy or UEFI) or through a bootloader supporting the Linux boot protocol.
- If the machine won't boot from the stick, check the boot order and whether the image was written to the raw device.
A useful next step: after creating the drive, test it on a machine you don't depend on first, then run it on the system you actually want to check. Expect a thorough pass to take a while, so plan to leave it running.
For download links and the full README, see Memtest86+.
What should I do if Memtest86+ reports RAM errors?
If Memtest86+ reports errors, treat them as a real hardware signal rather than a software glitch. The tool is designed to detect faulty RAM with multiple algorithms, so a reported failure usually means at least one memory module is not reliably storing data. Your first goal is to confirm the error and narrow down which module or configuration is responsible.
Immediate steps
- Re-run the test once more. Boot from the same USB drive and let it complete at least one full pass. A single error can occasionally come from a bad boot medium or an unstable overclock, so a second run helps confirm the result.
- Write down the details. Note the test number, the failing address range, and whether errors cluster in one region or appear randomly. This pattern helps distinguish a failing stick from a timing or voltage problem.
- Reset to defaults. If you have overclocked your CPU or RAM, or enabled an extreme XMP/EXPO profile, load BIOS/UEFI defaults and test again. Instability from overclocking is a common cause of errors that disappear at stock settings.
- Test modules one at a time. Remove all but one stick, run the test, then repeat for each module in the same slot. This isolates a single faulty stick from a slot or compatibility issue.
- Swap slots. If a module fails in one slot, try it in another. If it passes elsewhere, the motherboard slot or its seating may be the problem.
- Re-seat and clean. Reseat the modules firmly and check for dust or bent pins. Poor contact can mimic a memory fault.
What the results usually mean
| Observation | Likely cause | Practical next step |
|---|---|---|
| Errors only with overclock/XMP enabled | Unstable memory profile | Run at default or a lower profile; test again |
| One module fails in every slot | Faulty module | Replace it under warranty |
| A module fails only in one slot | Motherboard slot or seating issue | Try another slot; inspect the slot |
| Errors across multiple modules | Incompatible kit, wrong voltage, or motherboard issue | Check QVL compatibility; test a known-good stick |
| Errors appear only after long runtime | Heat or marginal stability | Improve cooling; re-test |
When to replace rather than troubleshoot
If a module fails consistently at stock settings, in more than one slot, and with a clean re-seat, it is faulty. Contact the manufacturer for a warranty replacement. For a new build or a server going into production, do not deploy until a full pass completes with zero errors.
A useful next step
Before replacing anything, run one more complete pass with a single module at BIOS defaults. That one test separates a genuine dead stick from an overclock or seating problem, and it gives you the exact evidence a warranty claim needs.
How is Memtest86+ different from Memtest86?
Memtest86+ and Memtest86 are two separate memory testing tools that share a confusingly similar name. Memtest86+ is a free, open-source stand-alone memory tester released under GPL v2.0. According to the project's own page, it is not an edition of Memtest86, which has been closed-source "freemium" software owned by PassMark Software since 2013. So the practical difference is licensing and stewardship, not just branding.
Practical differences
| Aspect | Memtest86+ | Memtest86 |
|---|---|---|
| Licensing | Free and open-source (GPL v2.0) | Closed-source, freemium |
| Maintainer | Community project (v6 code base originated as PCMemTest by Martin Whitaker, based on v5 by Sam Demeulemeester) | PassMark Software |
| Cost | Free | Free tier plus paid editions |
| Audience | Users who want an open, freely redistributable tester | Users who want vendor-supported tooling |
Both boot outside your operating system to test RAM directly, and both are aimed at the same job: diagnosing faulty memory that causes crashes, freezes, BSODs, and instability. Memtest86+ states it provides a more thorough check than BIOS memory tests, and it supports IA-32, x86-64, and LoongArch64 systems, loading via legacy BIOS, UEFI, or a Linux-protocol bootloader.
Which to choose
Pick Memtest86+ if open-source licensing matters to you, if you want to inspect or redistribute the tool, or if you simply want a no-cost tester without paid-tier prompts. Consider PassMark's Memtest86 if you specifically want commercial vendor support. For most home troubleshooting—random crashes, a new build, or a fresh overclock—either will tell you whether your RAM is faulty; the deciding factor is usually the license, not the test result.
A useful next step: before running a long test, make sure your USB drive is FAT32-formatted (for the Windows installer route) or write the ISO directly to the raw device with dd or a utility like balenaEtcher on Linux and macOS, then select the drive from your boot menu.
Should I run Memtest86+ on a new PC or after overclocking RAM?
Yes. Memtest86+ is designed for exactly these two moments: checking a brand-new machine before you trust it with real work, and validating stability after changing CPU or RAM settings. Its page explicitly frames testing as a way to "ensure initial stability" before putting a new PC or server into production, and after overclocking the CPU or RAM.
Why it's worth the time
Memory errors are a common cause of crashes, freezes and general instability. A BIOS memory test is much shallower than what Memtest86+ runs, so a machine that passes POST can still fail under load. The tool is a stand-alone, free, open-source tester for IA-32, x86-64 and LoongArch64 systems, licensed under GPL v2, and it runs directly from BIOS (legacy or UEFI) or through a Linux-protocol bootloader.
What each scenario actually needs
| Scenario | What you're checking | Practical approach |
|---|---|---|
| New PC or server | Whether the RAM is faulty out of the box or mismatched with the board | Run at stock settings before installing your OS or data |
| After overclocking RAM or CPU | Whether the new settings are genuinely stable, not just bootable | Run a full pass; a quick pass only proves it boots |
| Random crashes, BSODs, freezes | Whether RAM is the culprit before replacing other parts | Test RAM first, since it's a common cause |
Practical notes
- Build the USB stick first. On Windows, use the provided USB installer with a FAT32 drive; on Linux, dump the ISO to the raw device with
ddor a tool like balenaEtcher; on macOS the page recommends balenaEtcher. - Plan for downtime. A thorough test takes time, so run it when you don't need the machine — ideally before you migrate data onto a new build.
- Test at the settings you intend to use. If you plan to run an overclock daily, that's the configuration to validate, not the stock one.
Next step
Decide based on consequence: if the machine will hold data you can't easily recreate, or will run unattended, test before it goes into service. If you only changed a fan curve or a case, skip it.
One clarification worth knowing: Memtest86+ is not an edition of Memtest86, which has been closed-source freemium software owned by PassMark since 2013. If you're following a guide, make sure it matches the tool you actually downloaded.
What are common causes and fixes for Memtest86+ booting issues?
Memtest86+ boot failures usually come from the boot medium itself, the firmware settings, or the way the image was written — not from the RAM being tested.
Common causes and fixes
- Image written as a file instead of a raw dump. On Linux and macOS the ISO must be dumped directly to the device (e.g. with
ddor balenaEtcher). Copying the ISO onto a mounted filesystem produces a USB drive that will not boot. On Windows, use the official USB installer on a FAT32-formatted drive, then pick that drive from the boot menu. - Secure Boot enabled. A self-built or unsigned boot stick can be rejected by UEFI firmware. Either disable Secure Boot temporarily or use a signed build where available.
- Wrong boot mode. Memtest86+ supports both legacy BIOS and UEFI on x86, but a stick prepared for one mode may not appear in the other. Try switching between UEFI and CSM/legacy in firmware settings.
- Boot order or fast boot. Fast Boot can skip removable devices entirely. Enter the firmware boot menu manually (often F12, F10, F8 or Esc at power-on) and select the USB entry explicitly.
- Incompatible or very new hardware. Very recent chipsets and CPUs sometimes need a newer build than the one on the stick. A nightly or dev build is the usual workaround.
- Faulty or marginal USB drive/port. Try another stick and a rear-panel USB 2.0 port; front-panel hubs and extension cables are frequent culprits.
A quick decision path
- Re-create the stick with a raw-dump tool rather than a file copy.
- Reboot straight into the firmware boot menu and select the USB device by name.
- If it still fails, toggle Secure Boot and the UEFI/legacy mode.
- If nothing boots, test a different USB drive and port.
- If the hardware is brand new, try a nightly build before assuming a hardware fault.
For reference material and the official installer links, see Memtest86+. For the raw-write utility recommended for macOS and Linux, see balenaEtcher.
One practical note: if the machine boots Memtest86+ but reports errors, that is a memory or settings problem rather than a boot problem — reseat the modules, drop memory speed or XMP/EXPO, and retest before replacing anything.
User reviews (0)