Take web-optimized VP8/VP9/AV1 WebM files and turn them into widely accepted H.264 MP4.
Drop video files here or click to browse
Files queue into the current batch until you convert · MP4, MOV, MKV, WebM, M4V
WebM is built for the web. Chrome's screen recorder produces it, OBS can output it, and many sites serve it for embedded video. The trade-off shows up the moment you try to use the file anywhere outside a browser. Premiere, Final Cut, DaVinci Resolve, iPhone Photos, Instagram, TikTok, and most TVs all expect MP4 with H.264. WebM either fails outright or triggers an extra server-side transcode that can degrade quality.
Converting WebM to MP4 is usually the last step before handing video off to another tool or uploading it. It swaps the web-optimized container for the format the rest of your workflow already speaks.
This converter handles the typical WebM sources (VP9 screen captures, downloaded clips, AV1 in newer browsers) and re-encodes them into H.264 MP4 in your browser.
WebM almost always wraps VP8, VP9, or AV1 video with Opus or Vorbis audio. The converter decodes these in the browser and re-encodes the video as H.264 with AAC audio inside MP4.
Sources: MDN: media container formats · Reviewed 2026-10-12
Instagram, TikTok, X, and most CMS uploaders accept MP4 with H.264 deterministically. WebM upload support varies and often triggers an extra server-side transcode that can degrade quality.
Chrome's built-in tab recorder and many browser extensions output VP9 WebM. These convert quickly because screen content compresses very well, and re-encoding to H.264 keeps text and UI elements crisp.
AV1 decoding depends on the browser and device. Safari requires Apple hardware with an AV1 decoder, while other browsers may use hardware or software paths. The converter can proceed only when the exact AV1 configuration is supported.
Sources: MDN: Web video codec guide · MDN: checking decoder support · Reviewed 2026-10-12
VP9 and AV1 are more efficient codecs than H.264. The converted MP4 can end up slightly larger than the WebM source at matched quality. Lower the quality preset if size matters more than fidelity.
Sources: MDN: Web video codec guide · Reviewed 2026-10-12
Some WebM clips carry a transparency channel. MP4 with H.264 does not preserve alpha, so the converted file will have a solid background.
Convert a folder of WebM files to MP4 in your browser without uploading anything.
Drag and drop one or many WebM files into the queue, or click to pick them.
Output is preset to MP4. Most WebM screen captures are already small, so leave the quality on the higher preset unless you specifically need a smaller upload.
Click Convert files. Each file is processed locally in your browser.
Download converted MP4 files individually, or grab the whole batch as a ZIP.
No. The conversion runs in your browser; the file stays on your device. There is no upload endpoint for video.
Current Safari versions support VP9 WebM, but older Apple devices and many editing or upload workflows still prefer H.264 MP4. AV1 support on Safari additionally requires Apple hardware with an AV1 decoder. MP4 remains the broader interchange format.
Sources: MDN: Web video codec guide · Reviewed 2026-10-12
Sometimes slightly. VP9 and AV1 are more efficient codecs than H.264 at matched quality, so an MP4 of the same source can be a little larger. Lower the quality preset if size matters more than quality.
Yes when the current browser and device support the file’s AV1 configuration. Support is checked at conversion time; Safari requires AV1-capable Apple hardware.
Sources: MDN: Web video codec guide · MDN: checking decoder support · Reviewed 2026-10-12
Conversion requires WebCodecs video encoding and decoding, but each browser and device supports a different codec subset. MP4, MOV, and MKV output use H.264 video with AAC audio; Firefox and desktop Linux browsers do not natively encode AAC. Safari 16.4 added video WebCodecs, while Safari 26 added audio encoding and decoding. WebM output uses VP9 with Opus and may work where AAC output does not. For the widest support, use a recent desktop Chrome or Edge release, or Safari 26+. The converter still validates the actual source and output codec configuration when a job starts.
Sources: MDN: WebCodecs API · MDN: WebCodecs codec selection · WebKit: WebCodecs video support in Safari 16.4 · WebKit: WebCodecs audio support in Safari 26 · Mediabunny: supported formats and codecs · Reviewed 2026-10-12
Drop in MOV files, including HEVC iPhone clips, and get MP4s back in one pass.
OBS recordings, screen captures, and rips. Turn folders of MKV into MP4 in one pass.
Turn MOV clips into VP9 WebM files for self-hosted web video.
Take heavy MKV captures from OBS and turn them into lean VP9 WebM ready for the web.
Drop in a folder of mixed-format videos. Pick one destination format. Download the whole batch.