What is the MSWMM file format?
.mswmm files are used by Windows Movie Maker to store projects created with this program. The file does not contain actual video and audio data or still images - only references to that media. Each file also contains titles, movie timelines, and settings for the movie.
Internally, .mswmm uses the OLE2 Compound File Binary format - the same container family as classic .doc and .xls - beginning with the signature bytes D0 CF 11 E0 A1 B1 1A E1 at offset 0. Its successor format, .wlmp, switched to plain-text XML instead.
Data stored in .mswmm can be combined and edited using Windows Movie Maker. Because only references to source clips are stored, all original media files must remain at their original paths for the project to open correctly.
.mswmm is not widely supported outside of classic Windows Movie Maker. It can be converted to formats such as .WMV, .AVI, .MOV, or .MP4 before sharing. Windows Movie Maker was discontinued, making .mswmm a legacy format that modern video editors do not open natively.
Security & safety
RISK: MEDIUMThe .mswmm file itself is harmless project data (an OLE2 compound file with paths and edits, no executable payload). The real risk is the software hunt: after Movie Maker's January 2017 EOL, countless fake 'Windows Movie Maker' download sites appeared bundling adware, PUPs and malware (some impersonated Microsoft and charged for the formerly-free app). If you must reinstall the classic Movie Maker to reopen an .mswmm, use only a copy you trust, not a search-ad 'free download' portal. Note the .mswmm also exposes full local file paths if shared.
Format details
in a nutshellFULL NAMEMicrosoft Windows Movie Maker Project
DEVELOPERMicrosoftsince 2000 (Windows Movie Maker, Windows Me); used through the XP/Vista era
CATEGORYVideo Files
MIME TYPEapplication/octet-stream
TYPEMovie Maker project file - references to source clips plus edits/effects/timeline; NOT a playable video (binary, OLE-based)
MAGIC BYTES · FILE SIGNATURE
OFFSET
0001020304050607
HEX
D0CF11E0A1B11AE1
ASCII
········
The classic (XP/Vista-era) .mswmm is a Microsoft OLE2 Compound File (the same container family as old .doc/.xls), so it begins with the compound-file signature D0 CF 11 E0 A1 B1 1A E1 at offset 0. It stores the project's structure and references to the source media, not the media itself. (Its later successor, .wlmp from Windows Live Movie Maker, is instead a plain-text XML file.)
Programs that open MSWMM files
Windows2 apps
Windows Movie Maker (classic, XP/Vista)
Free The only program that opens .mswmm: File > Open Project, then 'Save Movie File' to export WMV/AVI. DISCONTINUED 10 Jan 2017 - official download removed; use a copy you already trust. Avoid scam re-download sites.
Hex / text inspection (e.g. 7-Zip on the OLE streams)
Open-source Not an editor - but because .mswmm is an OLE2 compound file, tools can peek inside to find the referenced source file paths if you need to locate the original media. Technical details
deep spec| Developer | Microsoft Corporation |
| File structure | OLE2 Compound File Binary (Microsoft Compound Document Format) |
| Magic bytes | D0 CF 11 E0 A1 B1 1A E1 at offset 0 (same signature used by classic .doc and .xls files) |
| MIME type | application/octet-stream |
| Media storage model | Stores references to external source clips only; no audio or video data is embedded in the file |
| Source path dependency | Project fails to load if source media files are moved or renamed after the project is saved |
| Timeline data | Records edit timeline, clip trim points, transitions, titles, and applied video effects |
| Native application | Windows Movie Maker (classic), available on Windows Me, XP, and Vista |
| Platform | Windows only; no macOS or Linux support |
| Successor format | .wlmp (Windows Live Movie Maker), which stores project data as plain-text XML rather than OLE2 binary |
| Export targets | WMV, AVI, MOV, and MP4 via Movie Maker's built-in Save Movie wizard |
| File size | Typically a few kilobytes; source media is stored externally and not embedded |
| Internal metadata encoding | Project settings and timeline data encoded as XML within named OLE2 compound streams inside the file |
| Current status | Legacy format; Windows Movie Maker was discontinued and .mswmm is not natively supported by modern video editors |
| Released | 2000 (Windows Movie Maker, Windows Me); used through the XP/Vista era |
MSWMM conversions
Possible
.MSWMM .MP4GUIDE
Yes - but it takes two steps: open the project in the classic Windows Movie Maker, export to WMV, then…
How to convert
.MSWMM .AVIGUIDE
Yes, you can get an AVI from an MSWMM project - but only by opening it in the classic Windows Movie Maker…
How to convert
.MSWMM .WMVGUIDE
You can get a WMV from an MSWMM file, but only by opening the project in the classic Windows Movie Maker and…
How to convert
Not possible
Community Q&A
asked by users
A
Frequently asked questions
Why won't my MSWMM file play as a video?
Because it isn't a video - it's a Windows Movie Maker PROJECT file that only records your edits and points to your original clips. To get a playable video you must open it in Movie Maker and 'Save Movie File' to export a WMV (or AVI).
How do I open an MSWMM file?
Only the classic Windows Movie Maker (XP/Vista era) opens .mswmm, and it was discontinued in January 2017. You need a trusted copy of that program plus the original source media still in place; the Windows 10 Photos app and Windows 11 Clipchamp cannot open it.
How do I convert MSWMM to MP4?
There's no direct converter. Open the .mswmm in the classic Movie Maker (with the original clips present), 'Save Movie File' to WMV/AVI, then convert that to MP4 with the free HandBrake or VLC. Without Movie Maker and the media, the video can't be produced.
I only have the MSWMM file - can I recover my video?
Only if you also still have the original clips/photos/music it references AND a copy of the classic Windows Movie Maker. The .mswmm stores no actual footage, so by itself it can't be turned back into a video.
What's the difference between MSWMM and WLMP?
Both are Windows Movie Maker project files. .mswmm is the older XP/Vista-era format (an OLE2 compound file); .wlmp is the newer Windows Live Movie Maker format (XML). Neither holds the actual video, and neither opens in modern Windows editors.
Why does Movie Maker say my media is missing when I open an MSWMM?
Because the project only stores paths to the source files. If those clips were moved, renamed, deleted, or the .mswmm was copied to another PC without them, Movie Maker can't find the footage to rebuild the project.
References
1Microsoft Support - Windows Movie Maker (discontinued)support.microsoft.com
2Microsoft - Clipchamp (current Windows video editor)www.microsoft.com
