Convert Video to MP4, WebM or MOV
MOV, MKV and WebM to MP4, or MP4 to WebM: streams copied without re-encoding when the file allows.
- Free
- No sign-up
- No watermark
- Runs in your browser
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Which format should you use?
A video file is a container (MP4, WebM, MOV, MKV) holding compressed streams, usually one video codec and one audio codec. A player has to understand both, which is why a file can open on your laptop and fail on your phone. If you are not sure which row you need, MP4 with H.264 and AAC is the safe answer.
| Format | Video / audio codecs | Plays on | Best for |
|---|---|---|---|
| MP4 | H.264 + AAC from this converter; the container also allows HEVC and AV1 | Every current browser, iPhone and Android phones, smart TVs, desktop players | Sending to anyone, social apps, importing into editors |
| WebM | VP9 + Opus from this converter; also VP8, AV1 and Vorbis | Web browsers; patchy on TVs, editors and older Apple devices | Video embedded on your own web pages |
| MOV | H.264 + AAC from this converter; cameras also write ProRes and HEVC in it | QuickTime and Apple devices; most editors import it | Final Cut Pro, or any tool that asks for a .mov |
| MKV | Almost any codec, plus several audio and subtitle tracks | Desktop media players and many TVs; support in browsers, phones and editors is uneven | Keeping a recording with all its tracks; convert before sharing |
MP4 and MOV here carry the same H.264 + AAC, so moving a file between them is usually a copy. A stream is copied only when its codec fits and its timing starts at zero; many exported files start their audio a few milliseconds earlier, and then that audio is re-encoded while the video is still copied. The converter writes one video and one audio track: a second language track or the subtitles inside an MKV are not carried over. Resolution and frame rate stay as they were.
How it works
Open the video. Drop a MOV, MKV, WebM or MP4 onto the box, or tap it to pick a file. The converter reads the headers and shows the container, codecs, resolution and length it found.
Pick the output. Choose MP4, WebM or MOV. Before anything runs, the page says whether the streams can be copied or must be re-encoded, and why. A file already in that format is flagged instead of converted into itself.
Convert and check. Press Convert and follow the progress bar, or cancel at any point. The finished file plays on the page so you can check picture and sound before you download it.
What you get
- A copy when a copy will do
- When a stream already fits the target, it moves byte for byte into the new container instead of being recompressed: no generation loss and no wait for every frame. The decision is per stream, so a clip whose audio must be redone still keeps its original video.
- It reports what it actually did
- The result says, for the video and for the audio, whether it was copied without re-encoding or re-encoded, according to what the conversion did with each stream, not a guess made before it started.
- Rotation carried over
- Phones often store a clip on its side with a flag telling players to turn it. The converter keeps that flag's orientation in the new file, so a portrait clip still plays portrait.
- Honest about dead ends
- An AVI, WMV or FLV is refused by name the moment you pick it, and a codec your browser cannot decode is named in plain words as soon as you press Convert, before a single frame is processed.
Questions people ask
How do I convert MOV to MP4?
Drop the MOV here, leave MP4 selected and press Convert. H.264 video and AAC audio are copied into the MP4 without re-encoding when their timing allows, and the result says if a stream had to be re-encoded instead. In our tests in Chrome on one desktop computer, a 10-second 1080x1920 H.264 MOV became an MP4 this way in under a second. Recent iPhones record HEVC by default; that video is re-encoded to H.264 when your browser can decode HEVC, which takes longer. Browsers can't decode ProRes, so export an H.264 version from your editor first.
How do I convert MKV to MP4?
Open the MKV and choose MP4. H.264 video and AAC audio are copied across when their timing allows; Opus audio becomes AAC and VP9 video becomes H.264. Only the main video and audio tracks are kept. Dolby (AC-3) and DTS soundtracks, common in movie MKVs, can't be decoded by most browsers.
Does converting a video lose quality?
Not when the file is repackaged: the streams are copied unchanged, so picture and sound are identical to the original. A re-encode is lossy like any H.264, VP9 or AAC compression. Video is re-encoded at a high quality setting, so the loss is hard to see, but converting the same file back and forth adds it up each time.
Should I use MP4 or WebM?
Use MP4 unless the video is going on your own website. MP4 with H.264 and AAC plays on essentially every phone, TV, editor and browser. WebM with VP9 and Opus is a web format: browsers handle it well, but many TVs, older Apple devices and editing apps do not.
How do I convert WebM to MP4?
Open the WebM and choose MP4. WebM usually carries VP8 or VP9 video with Opus or Vorbis audio, which MP4 players don't expect, so both streams are re-encoded to H.264 and AAC; that takes longer than a MOV to MP4 repackage, because every frame is compressed again. Resolution and frame rate stay as they were.
Will the new file be bigger or smaller?
A repackaged file comes out almost exactly the same size, because the streams are the same bytes in a different wrapper: our 10-second test MOV of 5,038,029 bytes became an MP4 of 5,032,103 bytes. A re-encode can be larger or smaller than the original, because the encoder's quality setting decides its size, not the source.
Can I convert a video on my iPhone or Android phone?
Yes, in a mobile browser with WebCodecs, such as a current Chrome on Android or Safari 26 or newer on an iPhone: open this page there, pick the video and save the result. Earlier Safari versions can decode the picture but not always the sound, which matters whenever the audio has to be re-encoded. A repackage does little work; a re-encode compresses every frame, so on a phone it takes longer and needs the page open and in front until it finishes.
Converted. Now make it vertical.
This converter changes the file format and leaves the frame alone. GPT-Video takes a landscape video, reframes it to 9:16 by following the speaker's face, and cuts it into captioned short clips. That runs on our servers as part of the paid product, not in this tab.
Related
Your file is processed on your device and never uploaded.