WebM to MP4 Converter
Convert WebM recordings to MP4 for universal device playback.
Best for sharing screen recordings or browser captures on any device.
Drop files here
or click to browse · paste from clipboard
Accepts .WEBM · Up to 1,000 files
How it works
Drop your files
Drag and drop, click to browse, or paste from clipboard. Up to 1,000 files at once.
Choose settings
Adjust quality, format, and other options to match your needs.
Click Convert
Everything runs in your browser via WebAssembly. WebM to MP4 Converter happens locally — no server involved.
Download
Download files individually or grab all at once as a ZIP.
Frequently asked questions
WebM is an open format designed for the web — Chrome and Firefox play it natively, but support on Apple devices, Windows Media Player, and most video editors is limited. MP4 with H.264 plays everywhere without plugins or format negotiation. If you need to share a WebM recording or export a screen capture, MP4 is the compatible choice.
WebM files contain VP8 or VP9 video and Vorbis or Opus audio. ffmpeg.wasm handles all four codecs and re-encodes them to H.264 video and AAC audio, which is the standard MP4 payload for broad device support.
Re-encoding from VP8/VP9 to H.264 involves transcoding, so there is a small quality reduction — this is unavoidable when changing codecs. At CRF 23 (Better) the difference is not visible on most content. Use Best (CRF 18) if you need to preserve as much quality as possible.
Quality controls the H.264 CRF (constant rate factor). Best (CRF 18) produces the sharpest image at the cost of a larger file. Good (CRF 28) cuts file size noticeably with a visible quality reduction on detailed footage. Better (CRF 23) is the balanced default.
WebM files recorded by screen-capture tools sometimes have a variable frame rate (VFR), which can cause audio sync issues in the MP4 output. If audio drifts out of sync, the source WebM may have been recorded with VFR. Very long WebM files from browser recordings may also have timing issues in the header that cause conversion to stall — try splitting them before converting.
No. Conversion runs entirely in your browser using ffmpeg.wasm. Your files do not leave your device at any point.