Convert to
Options
Quality when re-encoding
We first try a fast copy with no quality loss and only re-encode when the codecs do not fit. Re-encoding long videos in the browser is slow.
Up to 500 MB · MOV, AVI, MKV, WebM, 3GP, FLV, MP4 · processed in your browser, nothing is uploaded.
First use downloads the processing engine (about 25 MB). It is cached afterwards.
How to convert a video to MP4
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Choose the target format
MP4 is selected by default and works on phones, TVs and social networks. Choose WebM if you need a web-friendly file from an MP4.
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2
Drop your video
Drag a MOV, AVI, MKV, WebM, 3GP or FLV file (up to 500 MB) onto the box, or click it to choose a file. Nothing is uploaded.
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3
Wait for the conversion
The tool first tries a fast copy with no quality loss. If the codecs do not fit, it re-encodes the video and shows the time left.
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Download the result
Press Download to save the converted file. The page tells you whether it was copied as it is or re-encoded.
Remux or re-encode: why some conversions take seconds
A video file is a container (MOV, MKV, MP4, AVI) holding a video stream and an audio stream. When the streams already use codecs that MP4 supports, such as H.264 video and AAC audio, converting is only a matter of moving them into a new container. This is called remuxing: it is very fast and does not change the quality at all.
When the codecs do not fit, for example an AVI with an old MPEG-4 codec or a WebM with VP9, the video has to be decoded and encoded again to H.264. That takes much longer in a browser and costs a little quality, so the tool only does it when needed and shows an estimate of the time left.
Common conversions
- MOV to MP4: iPhone and Mac recordings are usually H.264 or HEVC in a MOV container, and often remux in seconds.
- MKV to MP4: MKV often holds H.264 with AAC or AC3 audio. Only the audio may need converting.
- WebM to MP4: screen recordings and browser videos use VP8 or VP9, which are re-encoded to H.264.
- AVI, 3GP and FLV to MP4: older formats usually need a re-encode to play on modern devices.
- MP4 to WebM: use it to embed a video on a web page with open codecs.
Limits of a browser-based converter
Everything runs on your device with WebAssembly, so your video is never uploaded, but it is also limited by your device memory and speed. Files are limited to 500 MB, and re-encoding a long full-HD video can take many minutes on a phone. Keep the tab open and the screen on while it works.
Video converter FAQ
How do I convert MOV to MP4?
Leave MP4 selected and drop your MOV file. iPhone MOV files usually already contain H.264, so they are copied into an MP4 in seconds without losing quality.
Is my video uploaded anywhere?
No. The conversion runs inside your browser with WebAssembly. Your file never leaves your device.
Why are some conversions fast and others slow?
When the codecs already fit MP4, the tool only repackages them (remux), which takes seconds. When they do not, the video must be re-encoded, which is slow in a browser. A time estimate is shown.
What is the maximum file size?
The limit is 500 MB per file. For long or large videos, use a desktop converter or cut the video first with the Video Cutter.
Does converting reduce the quality?
Not when the video is remuxed: the streams are copied exactly. When it is re-encoded, quality drops slightly. Choose High under Options to keep as much detail as possible.
Which formats can I convert?
MOV, AVI, MKV, WebM, 3GP, FLV, WMV and MPEG to MP4 (H.264/AAC), and MP4 to WebM.