On some Windows machines, VLC hangs for roughly 10 to 33 seconds before it starts playing a media file, most visibly when an MP3 is opened directly from File Explorer. VideoLAN attributes this to Microsoft Defender quarantining or locking VLC's plugin cache file (plugins.dat) in the VLC installation folder; without a readable cache, VLC falls back to scanning its entire plugins directory on every launch, which is what produces the long hang.
The bug became widely discussed in August 2026 after game designer Jonathan Blow criticised VLC's performance publicly and VideoLAN responded that a Windows 11 Defender update, not VLC's code, was responsible. Note that the Defender attribution comes from VideoLAN and press coverage, not from Microsoft: as of 17 August 2026 there is no Microsoft advisory, KB article, Defender detection name, or affected security-intelligence version confirming it, and slow-startup reports of this kind predate the August 2026 discussion by well over a year. Treat the root cause as credibly reported but not vendor-confirmed.
Steps to reproduce:
- Use a Windows 10 or Windows 11 machine with Microsoft Defender enabled and no exclusion for the VLC folder.
- Install VLC media player and let Defender complete a background scan of the installation folder (or apply the Windows update that triggers the quarantine).
- Double-click an MP3 file in File Explorer so it opens in VLC.
- Observe that VLC's window appears but playback does not begin for roughly 10-33 seconds. The delay repeats on subsequent launches as long as the plugin cache stays unusable.
Workaround: Add the whole VLC installation folder (typically C:\Program Files\VideoLAN\VLC) to Microsoft Defender's exclusion list — several users report that excluding only vlc.exe is not enough — then regenerate the cache so the delay does not come back. Restoring the quarantined cache file from Defender's quarantine, or using a different antivirus product, is also reported to work.
Severity: Medium (makes a core, everyday action unusably slow on affected machines and recurs after each trigger, but causes no crash, data loss, or security exposure, and simple workarounds exist)
First seen: August 2026
Affected product: VLC media player
Affected platforms: Windows 10 and Windows 11 with Microsoft Defender enabled
Affected versions: Not precisely identified by any source; reports involve current VLC 3.0.x releases on Windows
Fixed versions: Not yet available
Links:
- https://x.com/videolan/status/2087590352350064835 (VideoLAN statement, ~13-14 August 2026)
- https://www.windowslatest.com/2026/08/14/vlc-blames-windows-11-bug-for-slow-performance-defends-open-source-and-calls-out-microsoft/ (14 August 2026)
- https://www.tomshardware.com/software/windows/vlc-media-player-bug-reportedly-causes-33-second-delay-when-playing-mp3-files-on-windows-developers-say-microsoft-defender-is-to-blame (~14 August 2026)
- https://www.techspot.com/news/113491-windows-defender-bug-making-vlc-take-30-seconds.html (15 August 2026)
- https://securityonline.info/microsoft-defender-vlc-bug/ (15 August 2026)
- https://windowsforum.com/windows-news.4/windows-11-defender-quarantine-may-delay-vlc-mp3-playback.442802/ (August 2026)
- https://www.windowscentral.com/software-apps/microsoft-defender-vs-vlc-which-is-causing-mp3s-to-take-30-seconds-to-load (August 2026)
- https://news.ycombinator.com/item?id=49073954 (August 2026)