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MP4 Converter

Turn videos that won't play or upload into MP4, the format every phone, TV, browser and social site accepts. Files already in H.264 are rewrapped in seconds with no quality change.

Converts MOV, MKV, WebM, M4V, 3GP and TS videos to MP4, up to 20 at a time. Runs on your device: the video is never uploaded. Works in Chrome, Edge, Opera and Samsung Internet (Android and computers), Safari 16.4 or later (iPhone, iPad and Mac; sound needs Safari 26), and Firefox 130 or later on computers. Firefox for Android can't encode video yet.

How to convert a video to MP4

  1. Choose one or more videos: MOV, MKV, WebM, M4V, 3GP or TS. Each shows its codecs and whether it will be rewrapped or re-encoded.
  2. Keep Plays everywhere for H.264 and AAC, or choose Fastest to keep the original codecs whenever MP4 can hold them.
  3. Press Convert to MP4 and download each file.

Rewrap or re-encode?

MOV, MKV and MP4 are containers: boxes holding a picture track and a sound track. When the tracks inside are H.264 and AAC, converting to MP4 only moves them into a new box, which is fast and lossless. VP8, VP9 and AV1 (common in WebM) and H.265 are re-encoded to H.264 with your browser's encoder, at about the original's bits per pixel, so the picture looks the same; sound that isn't AAC or MP3 is re-encoded to AAC at 160 kbit/s.

Example

A 720p WebM screen recording with a VP9 picture at 2 Mbit/s and Opus sound: VP9 is more efficient than H.264, so the MP4's picture gets 1.4 × 2 = 2.8 Mbit/s to look the same, and the sound becomes AAC. A 10-minute 1080p MKV from OBS with H.264 and AAC is rewrapped into an MP4 without re-encoding.

By format

  • MOV (iPhone, cameras): usually H.264 or H.265 with AAC; H.264 is rewrapped.
  • MKV (OBS, downloads): often H.264 and AAC, rewrapped; Dolby Digital sound is kept or re-encoded where the browser can decode it.
  • WebM (browsers, screen recorders): VP8 or VP9 with Opus, re-encoded to H.264 and AAC.

To convert to WebM, MOV or MKV instead, use the Video converter. To make the file smaller, use Compress video.

Video files are read and written with Mediabunny 1.61.3 (Mozilla Public License 2.0), loaded unmodified as a separate file, and coded by your browser's own video and audio encoders (WebCodecs). Licence and source code.

Frequently asked questions

Why convert a video to MP4?

MP4 with H.264 video and AAC sound plays on every phone, computer, TV and browser, and every social site and messaging app accepts it. MOV files from iPhones, MKV files from screen recorders and WebM files from browsers often won't play or upload somewhere; as MP4 they will.

Why is my MKV or MOV done in seconds?

If its picture is already H.264 and its sound AAC or MP3, nothing needs re-encoding: the tracks are copied into an MP4, so the quality is identical and it's only as slow as reading the file. OBS recordings in MKV and many camera MOV files are like this.

My iPhone video is HEVC. Will it work?

Yes, where your browser can decode H.265 (HEVC): Safari, Chrome and Edge on most Macs and on Windows PCs with HEVC support, and many Android phones. It's re-encoded to H.264 so it plays everywhere. Where H.265 can't be decoded, the tool rewraps it into an MP4 unchanged and says so.

Can I convert AVI or WMV to MP4?

Not in a browser: AVI and WMV use codecs browsers can't decode. Use VLC (free) on a computer for those. This converter reads MOV, MKV, WebM, M4V, 3GP, TS and MP4.

Is there a limit, and is anything uploaded?

Up to 20 files of up to 2 GB each, converted on your device. Nothing is uploaded, so there's no queue and no file-size plan to buy. Rewrapping needs no video encoder, so it works even in browsers that can't re-encode video, such as Firefox for Android.

More video and audio tools

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