Turn browser recordings and WebM clips into widely compatible H.264/AAC MP4 video. Free with clearly published fair-use limits — no sign-up, no watermarks.
Drop your WebM file here
or click to browse — One file per media job — 100 MB / 10 minute limit
☁️ Server conversion — your file is uploaded securely (HTTPS), converted, and removed from temporary processing storage after the request finishes. Forced-crash leftovers are removed by recovery sweeps. A verified codec/duration report is included on the download page. Which tools upload, and which do not
Browsers, screen recorders and meeting tools often create WebM files, while editors, messaging apps, televisions and upload forms commonly expect MP4. This is a real transcode — not an extension rename: FFmpeg decodes the source and writes H.264 video with AAC audio, then ffprobe reopens the result to verify the promised streams and duration.
This page has a real two-second fixture made from generated motion, colour and tones — no copyrighted clip and no visitor data. Download the source, run it through the tool, and compare it with the expected profile-1.0.0 output.
⬇ Sample input (WebM) ⬇ Verified expected output
| Check | Input | Expected output |
|---|---|---|
| Codecs | vp9 + opus | h264 + aac |
| Duration | 2.008 s | 2 s (Δ 0.008 s) |
| File size | 93,031 bytes | 89,611 bytes |
| SHA-256 | 834490a1a8b57748d371d0da60aa553b69f8ccfd3753093a1f8eff657180dae2 | 69b3ec972990330e85df6b4d2e8875de339877421fa0753e3cac7f6214c5ea46 |
| Measured time | — | 162 ms in the published environment |
| Validation | Signature + ffprobe | Codec, complete decode and duration: pass |
No confidence score is invented: transcoding is deliberately lossy, so the defensible result is a set of pass/fail structural checks, not “97% accurate.” Your download page exposes the same per-job evidence report as JSON and CSV. See the method, limitations and six-case comparison, or download the anonymous CSV / JSON dataset.
“Accuracy” for this lossy task means the published structural gates below; perceived quality still needs human review of the output.
| Profile | Date | Validation change | Re-test | Result |
|---|---|---|---|---|
| 1.0.0 | 2026-08-16 | Fixed codec profile; EBML DocType / ISO brand checks; rotation-aware dimensions; ffprobe; complete decode; duration tolerance | FH-MEDIA-01 plus the six-profile release gate and adversarial regressions | pass |
WebM is the browser-native media container used by screen recorders, webcam apps, meeting tools and web downloads. It commonly carries VP8 or VP9 video with Opus or Vorbis audio. Browsers handle it well, but many phone editors, televisions, messaging apps and upload forms still require MP4 or MP3 instead.
MP4 is the safest delivery container for video. The widely supported combination is H.264 picture with AAC sound, which plays on current phones, browsers, televisions and editing apps. MP4 can contain other codecs too, so a genuine compatibility conversion must inspect and encode the streams rather than merely rename the extension.
| WebM | MP4 | |
|---|---|---|
| Type | Video/audio container | Video/audio container |
| Compression | VP8/VP9/AV1 + Opus/Vorbis | Usually H.264/H.265 + AAC |
| Transparency | Codec-dependent | Usually no |
| Animation | Video | Video |
| Typical use | Browser recordings, web video, meetings | Sharing, uploads, playback, editing |
WebM is the natural output of browser screen recorders, webcam apps, Chromebooks and many online meeting tools. It plays beautifully where it was created, then often stops at the next boundary: a phone editor refuses it, a social upload form wants MP4, or a television sees no playable video. H.264 video with AAC audio inside MP4 is the practical delivery combination for crossing those boundaries.
This conversion does more than change a filename. FFmpeg decodes the WebM picture and sound and writes new streams, so some generation loss is unavoidable; fine screen text and fast motion are the first places worth checking. Keep the WebM as the source, open the MP4 from beginning to end, and use the converted copy for distribution rather than treating it as a new editing master.
Yes — there is no sign-up, payment or watermark. The published safeguards are 100 MB input, a 160 MB output cap, a 10 minute selected-stream limit, an 8 minute request-wide deadline and four jobs per visitor per 10 minutes; they are technical limits, not a paid tier.
Media files are handled one at a time. That makes the documented CPU, memory and cleanup limits enforceable and gives the next file a clean job directory. Finish or clear the current file before adding another.
Yes. Native FFmpeg is too large and resource-intensive for a reliable browser-only conversion, so this tool sends the file over HTTPS to our server. It is limited to 100 MB and 10 minutes and uses an isolated temporary job directory. Normal cleanup removes that directory after success, failure, cancellation or timeout; startup and five-minute sweeps remove a forced-crash leftover once it is older than the request deadline. Media files are never intentionally retained.
No. WebM and MP4 are different containers and usually carry different codecs. Renaming only changes the label; this tool decodes the source and writes a genuine MP4 with H.264 video and AAC audio.
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