WebM to MP4 Converter Online (also MOV, MKV, AVI → MP4) — Free, No Upload, No Size Limit
Drop a video here
or click to choose (WebM, MOV, MKV, MP4, AVI…)
processed in your browser · never uploaded
Converts in your browser — the file never leaves your device, so there is no upload wait and no size limit.
A free online tool to convert screen recordings (WebM), iPhone/Mac footage (MOV), MKV or AVI files to MP4 without installing a converter — and without uploading anything. Drop a video, see its format, codec, resolution and length, and press Convert to get an MP4 (or WebM). It works in two tiers. If the original video stream can live inside MP4 as-is (H.264, H.265, AV1…), the tool simply rewraps it: no re-encoding, done in seconds, zero quality loss. If the stream is VP8/VP9 (typical for WebM), the Compatible setting re-encodes it to H.264/AAC so the result plays everywhere: iPhone, QuickTime, PowerPoint, WhatsApp and old TVs. Pick Keep original (fast) instead for an always-lossless copy when the video only needs to play in Chrome-based apps. The big difference from typical online converters: the file never leaves your device. Everything runs locally via WebCodecs, so multi-GB files have no upload wait, and there is no account, queue or watermark. Audio is carried over as-is when possible; untick keep audio for a video-only MP4. A recent Chrome or Edge is recommended.
How to use
- Drop in a video file (WebM, MOV, MKV, AVI, MP4…).
- Choose the output (MP4 / WebM) and codec (Compatible / Keep original). Untick keep audio if you only need the picture.
- Press “Convert”, then download the MP4.
FAQ
Is my video uploaded?
No. Loading, converting and exporting all happen inside your browser on your device — nothing is sent to or stored on a server. That's why there is no upload wait and no size limit. Leaving the page discards any in-progress data.
Does converting WebM to MP4 lose quality?
With Keep original (fast) the video stream is copied without re-encoding, so quality is identical. Compatible re-encodes to H.264 only when the source codec (VP8/VP9…) isn't a standard MP4 codec, using a high-quality setting — the difference is normally invisible. An H.264 MOV or MKV is copied even in Compatible mode.
Compatible or Keep original — which should I pick?
When in doubt, Compatible: you get an H.264/AAC MP4 that plays on iPhone, QuickTime, PowerPoint, WhatsApp, smart TVs and basically everything. Keep original is instant and lossless, but an MP4 carrying VP9 won't open in QuickTime and some apps. If the video only needs to play in Chrome-based apps, Keep original is fine.
Can it handle large files (several GB)?
There is no size cap because nothing is uploaded. A lossless rewrap of a large file takes seconds. If re-encoding is needed, time scales with length and resolution and memory use grows, so for very long videos it's safest to cut out the part you need first with the Video Trim tool.
What happens to the audio? My converted file has no sound.
Audio is normally carried over untouched. Non-standard MP4 audio (Opus/Vorbis) is converted to AAC in Compatible mode. If your browser can't carry the audio track, the tool tells you and exports video-only — try the latest Chrome or Edge in that case.
Which browsers are supported?
Conversion uses WebCodecs, so a recent Chrome or Edge (or another Chromium-based browser) is recommended. Safari and Firefox may be unable to re-encode some codecs. Unsupported browsers get a clear error instead of a broken file.