Convert a video to MP4, MOV, MKV or WebM locally - lossless where possible, re-encoded otherwise. The video never leaves your device. No upload.
Running locally on your device ...
Running locally on your device ...
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Your files never left your device
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No re-upload neededThese tools accept .MP4 - your file is handed over directly.
No. Everything runs in your browser - your file never leaves your device. How this is verifiable
Whether it's an iPhone video that needs to be an MP4, an MKV that needs to become WebM for the web, or a WebM file that needs to play everywhere as MP4 - this one tool converts between MP4, MOV, MKV and WebM. You just pick the target format; the tool handles the rest automatically.
Behind the scenes this happens the fastest possible way: if the existing codec fits the target container, only the wrapper is swapped - lossless and in seconds, without recomputing picture or sound. If it doesn't fit (e.g. an H.264 file to WebM), the tool automatically re-encodes using your browser's native WebCodecs encoder - you won't notice anything except the result.
Honest edge case: re-encoding is only possible when the target is MP4 or WebM. If the codec doesn't fit MOV or MKV and a re-encode would be needed, we say so clearly - try MP4 or WebM instead in that case.
Everything runs locally in your browser - partly with ffmpeg (self-hosted, no third-party CDN), partly with your browser native video encoders via WebCodecs (mediabunny, MPL-2.0). Your video is not uploaded.
Other free online video converters upload your file to a server, cap the file size at a few hundred megabytes, or require an account after a handful of daily conversions. None of that applies here: conversion runs unlimited and free, with no account and no watermark, because everything happens in the browser instead of on a foreign server. That works on any device with a modern browser - Windows, Mac, Linux, even a Chromebook or smartphone.
| Input formats | MP4, M4V, MOV, MKV, WEBM |
|---|---|
| Auto-conversion | PNG, GIF |
| Output formats | MP4, MOV, MKV, WebM |
| Batch processing | No |
| Processing | Locally in your browser (WebCodecs) |
| File upload | None |
Limitations: Re-encoding (when the codec does not fit the target container) is only possible for MP4 and WebM - for MOV/MKV you get an honest error instead of a silent re-encode. Picture and sound stay unchanged for a lossless remux; a re-encode produces a new, slightly lossy encoding at unchanged resolution (for compression with selectable resolution/quality, use the sibling tool "Compress video"). Subtitle tracks only survive the lossless remux path (there every track is copied, just like every audio track); when a re-encode is needed, that path only ever reads and writes picture and sound, so subtitle tracks are lost. One file per run, ~1 GB limit (4 GB/tab in the browser).
| Format | Compatibility | Remux possible? | Re-encode possible? |
|---|---|---|---|
| MP4 | very broad | yes, if the codec fits | yes |
| MOV | Apple/QuickTime | yes, if the codec fits | no (honest error) |
| MKV | container for any codec | yes, if the codec fits | no (honest error) |
| WebM | web (VP8/VP9/AV1 + Opus/Vorbis only) | yes, if the codec fits | yes |
No. The whole conversion happens locally in your browser.
Only if a re-encode is needed (the codec does not fit the target container) - then yes, slightly. If the codec fits, it is a lossless remux.
A lossless remux (codec fits) finishes in seconds. A re-encode (codec does not fit) takes longer because picture and sound are fully recomputed.
Use the sibling tool "Compress video" for that - resolution and quality are selectable there.
WebM only allows VP8/VP9/AV1 and Opus/Vorbis. An H.264/AAC file does not fit - the tool then automatically re-encodes instead of producing a broken file.
Yes. Any current mobile browser with WebCodecs support (such as Chrome on Android) works the same as on desktop - the file stays just as local on the device.
No. No account, no daily limit, no watermark - conversion is unlimited and free because it never touches a server.
Yes - with gottrix, "online" just means "in your browser," not "on someone else's server." Your video never leaves your device; try airplane mode, the conversion keeps working.
Compress video · Video to GIF · Trim video · Analyze a media file · Edit video · Remove video audio