Windows Memory Diagnostic

What Windows Memory Diagnostic is

Windows Memory Diagnostic is a free, built-in utility that tests your installed RAM modules for hardware errors. It runs a series of read/write pattern tests against physical memory outside of the normal Windows environment, since memory that's actively running the operating system can't be tested reliably from within it. The tool reboots the PC into a minimal diagnostic environment, runs its tests, then boots back into Windows and reports whether it found any faults.

It's aimed at diagnosing symptoms like random blue screens, freezes, or application crashes that don't seem tied to any specific piece of software, since those are classic signs of failing or improperly seated memory.

What mdsched.exe does

mdsched.exe is the executable behind Windows Memory Diagnostic — running it is the tool. Launching mdsched.exe opens a small dialog offering to restart immediately or schedule the test for the next reboot; it doesn't test anything while Windows is still running. Once the reboot happens, a separate pre-boot diagnostic environment (not Windows itself) actually performs the memory tests.

How to launch it

• Run dialog: press Windows key + R, type mdsched.exe, and press Enter.
• Search: press the Windows key, type Windows Memory Diagnostic, and select the result.
• Command line: open Command Prompt or PowerShell and run mdsched.exe (no elevation required to launch, though the diagnostic itself runs at reboot).

Command reference

mdsched.exe
mdsched /?

Running it on Windows 10

1. 1Press Windows key + R, type mdsched.exe, and press Enter.
2. 2Choose Restart now and check for problems (recommended), or Check for problems the next time I start my computer.
3. 3Windows saves open work reminders aside — save your files first, since it restarts immediately with the first option.
4. 4After reboot, the test runs automatically; results appear in a popup after Windows loads, or in Event Viewer if missed.

Running it on Windows 11

1. 1Press Windows key, type Windows Memory Diagnostic, and open it (or use mdsched.exe via Run).
2. 2Select Restart now and check for problems (recommended) to test immediately.
3. 3The steps and diagnostic screen are functionally identical to Windows 10 — Microsoft hasn't changed mdsched between the two versions.
4. 4After the automatic reboot, check the results popup or Event Viewer as with Windows 10.

What happens at reboot

The PC restarts into a blue, text-based diagnostic screen separate from Windows — this is the Windows Memory Diagnostic Tool environment, not the OS. It begins running the default Standard test mix immediately. A status bar shows progress, current pass number, and the test currently running. When it finishes, the PC reboots again automatically back into Windows; you don't need to do anything unless you want to change test options.

Standard vs extended test options

Press F1 during the blue diagnostic screen to open the Options screen, which lets you configure the test before it runs (or re-run with different settings).

How long the test takes

Duration depends mainly on RAM size, test mix, and pass count, since more memory means more data to read and write per pass.

Where and how to read results

If you're at the PC when the test finishes and Windows finishes loading, a notification popup usually reports the outcome directly. If you miss it or the popup doesn't appear, the result is still logged and can be found manually.

1. 1Open Event Viewer (press Windows key, type Event Viewer).
2. 2Expand Windows Logs and select System.
3. 3Click Filter Current Log in the right-hand pane.
4. 4Enter MemoryDiagnostics-Results in the Event sources field, or filter by Event ID 1201 (test completed).
5. 5Open the matching event to read the pass/fail summary.

Interpreting results

A clean pass with no errors reported means the tool didn't detect faults during that specific run — it's a good sign but not an absolute guarantee, since intermittent errors can be missed by a limited number of passes. Any reported hardware errors indicate faulty or improperly seated RAM and should be treated seriously; don't dismiss a single error as a fluke.

Limitations

• It can miss intermittent faults that only appear under extended, repeated stress — a clean Standard-mode result doesn't rule out a marginal module.
• It only tests RAM; it does not test the CPU, motherboard, storage, or power supply, even though those can cause similar instability symptoms.
• It requires a reboot and can't run in the background while you keep working.
• It offers less test-algorithm variety than dedicated third-party memory testers.

Alternatives for deeper testing

MemTest86 is a well-known independent, third-party memory tester (not part of Windows or Microsoft) that boots from USB outside any OS and runs a broader set of test algorithms than mdsched, often over many hours or overnight. It's worth using when Windows Memory Diagnostic comes back clean but symptoms persist, or when you can't boot Windows reliably at all.

For full walkthroughs of both tools, see our guide on how to test RAM on Windows.

What to do when errors are found

• Reseat each RAM module — remove and firmly reinstall it in its slot, since a poor connection alone can cause errors.
• Test one stick at a time with the other modules removed to isolate which specific stick is faulty.
• Try each stick in a different slot to rule out a bad motherboard slot rather than a bad module.
• Turn off XMP/EXPO memory overclocking profiles and any manual overclock in BIOS/UEFI, then retest at stock/JEDEC speeds — unstable overclocks are a common false-positive source.
• If errors persist at stock settings with a single known-good stick, the module itself is likely faulty and should be replaced.