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Mapset Verifier (MV) is a desktop app which tests quantifyable issues in beatmapsets from osu!, such as unsnapped objects and unused files. Many of these issues would otherwise disqualify the map from being ranked. Although mainly aimed at Beatmap Nominators, this can also be used by mapset creators and reviewers to speed up the ranking process.
MV is a successor to the game's built-in AiMod and Sieg's Modding Assistant, providing more features and greater scalability. Some examples include auto-updates, plugin support, and integrated documentation and diff utilities.
MV 2.0 is a ground-up rewrite of the application: New React frontend, updated .NET 9 backend, a ton of new features, and built-in checks for all game modes!
This is currently being ported to osu!lazer. You can track its progress here!
Warning
Some issues are not easily quantified, especially ones related to metadata and timing; far from everything is covered. Also, false positives and false negatives may occur, as with any similar tool. So always use your own judgement and be critical about what the program points out, especially warnings.
Get the latest build from mv.mappersguild.com/releases.
The website has release notes, screenshots, and platform-specific install instructions. On Windows, grab the installer (.exe). On Linux, use the AppImage or the Arch AUR package. On macOS, use the DMG or ZIP.
GitHub also hosts every release under Releases.
Older versions (MV 1.x)
These builds are from the pre-2.0 release line. Prefer the current download page unless you specifically need 1.x.
| Version | Date Released | Windows | Linux |
|---|---|---|---|
| 1.8.2 | 2021-09-21 |  |
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| 1.8.0 | 2021-09-14 |  |
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| 1.7.2 | 2020-10-07 |  |
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| 1.7.1 | 2020-10-03 |  |
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| 1.7.0 | 2020-09-28 |  |
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| 1.6.6 | 2020-08-04 |  |
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| 1.6.5 | 2020-07-03 |  |
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Windows SmartScreen / "Windows protected your PC"
- Fix: Click More info → Run anyway, or right-click the installer → Properties → check Unblock.
- Why: The installer is not code-signed (signing certificates are expensive).
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App fails to start — backend executable missing (
ENOENT)- Fix: Uninstall, reinstall, and whitelist
MapsetVerifier.exein your antivirus before launching again. The backend lives underbin/server/dist/<platform-arch>/inside the installed app (for examplewin-x64on 64-bit Windows). - Why: Some antivirus tools flag the backend on first run and delete it before MV can use it.
- Fix: Uninstall, reinstall, and whitelist
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MV 1.x plugins do not load on MV 2.0
- Fix: Rebuild plugins for .NET 9 against the current API, or remove legacy DLLs. Many former mode-specific plugins are now built into MV 2.0.
- Why: MV 2.0 changed the runtime, folder layout, and check API. See Custom checks documentation.
MV supports custom check plugins (.dll files) that run alongside built-in checks. Install paths, the check API, security notes, and migration guidance from MV 1.x are documented in the custom checks documentation.
Only install plugins from sources you trust — they run inside the backend process with the same privileges as the application.
To build from source, package releases, or learn how the stack is put together, see the development documentation.
Open a GitHub issue with the beatmapset link and steps to reproduce when you can.
You can also reach the current maintainers directly on osu!: