winmm.dll not found or crashing: what the Windows Multimedia file is and how to fix it

Every file here is Microsoft's own winmm.dll for one Windows release, taken from Microsoft's symbol server and matched against Winbindex, the public index of files in Windows releases and updates. Check your release in Settings, System, About, then pick the 64-bit build (System32) or the 32-bit build (SysWOW64). For a working PC the steps above are the better route: Windows guards both folders and updates the file by itself. These downloads are for comparing a copy you already have, or for a repair that System File Checker and DISM could not finish.

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Read the message before you change anything: each text points to a different place. Below are the texts Windows uses, with the file name as Windows writes it.

winmm.dll holds the Windows Multimedia API, the sound and timing interface Windows has offered since the 1990s. Programs call it to play and record wave audio (the waveOut and waveIn functions), to send and receive MIDI, to play sounds with PlaySound, to control media devices through MCI commands, which older games used to play music from CD audio tracks, to read simple joysticks, and to use the multimedia timers, such as timeGetTime and timeBeginPeriod, that many games use to pace frames. Newer audio interfaces sit beside it, but Windows keeps winmm.dll so that old and new software still runs. What Windows reports for the genuine file:

On 64-bit Windows the 64-bit library is in System32 and the 32-bit library in SysWOW64. When a program starts, Windows checks the program's own folder for winmm.dll before it checks System32, and loaders and wrappers rely on exactly that: a file with this name beside the .exe is loaded first and then passes calls on to Windows' copy. The genuine file is signed by Microsoft and describes itself as MCI API DLL. In Windows 11 24H2 and 25H2 the 64-bit file is 240,912 bytes and the 32-bit file 213,144 bytes; in Windows 10 22H2 they are 148,376 and 150,352 bytes. A game folder copy usually has a different description and size and no Microsoft signature.

Windows updates winmm.dll together with the rest of the system, and each release has its own build. Winbindex knows 421 different Microsoft builds; the table shows the newest one indexed for each release and the update it came in. For a few Windows 10 releases the newest indexed 64-bit build is a very small file of about 10 KB; it is still a Microsoft build.

Public DLL catalogues hold 16 copies of winmm.dll that people uploaded from their PCs, from version 4.3.0.1998 to 10.0.18362.1. Most belong to older Windows releases. The table gives the checksums of each, so you can identify the one you have.

None of them is a substitute for the build your Windows ships: the newest build indexed for Windows is 10.0.28000.2605, and every release has its own. If the check on this page finds your file here, it is most likely an older Microsoft build that someone copied by hand. Confirm the Microsoft signature, remove the copy from the program folder, and let Windows use its own.

Copies uploaded by users to a public DLL catalogue, read on 14 October 2026. The checksums help you identify a file; we do not offer these copies for download and did not check each one against Microsoft's signature.