Video Converter: Convert Video to MP4 or WebM
Convert MP4, MOV, WebM and MKV videos to MP4 or WebM in your browser. Compatible videos are converted without re-encoding, so there is no quality loss. No upload.
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Your files never leave your device
About this tool
This video converter changes the container and, when needed, the codecs of a video so it opens where you need it. Drop an MP4, MOV, WebM or MKV file and convert it to MP4, the format every phone, browser and editor plays, or to WebM, the open format made for web pages. Everything happens in your browser, so the file is never uploaded.
How to convert a video
- Drop the video on the page or click to choose it.
- Pick MP4 or WebM under Convert to. The panel tells you whether the video can be copied as is or must be re-encoded.
- If re-encoding is needed, choose High quality or Balanced.
- Click Convert to MP4 (or WebM), check the preview and the new size, then download.
Copy or re-encode?
A video file is a container holding a video stream and an audio stream. Often only the container is the problem: an MKV or MOV with H.264 video already has exactly what an MP4 needs. In that case the converter simply copies the streams into the new container. This takes seconds, even for long videos, and the picture stays bit for bit identical.
| Source codecs | To MP4 | To WebM |
|---|---|---|
| H.264 + AAC (most MP4, MOV, MKV) | Copied, no quality loss | Re-encoded to VP9 + Opus |
| VP9 or VP8 + Opus (most WebM) | Re-encoded to H.264 + AAC | Copied, no quality loss |
| H.265 / HEVC (recent iPhones) | Re-encoded to H.264 | Re-encoded to VP9 |
| H.264 + AC-3 or FLAC audio | Video copied, audio to AAC | Re-encoded |
Tips for the best result
- Choose MP4 when in doubt. It is the safest choice for WhatsApp, Instagram, PowerPoint, TVs and video editors.
- Choose WebM for websites when you want an open format for an HTML5 video tag.
- Surround sound is mixed down to stereo when the audio has to be re-encoded, which keeps the file small and plays on every device.
- Large files work too: the limit is your device's memory, not an upload size.
Private by design
The conversion uses your browser's built-in media engine (WebCodecs) and your device's hardware encoder. The video never leaves your computer or phone. Need a smaller file afterwards? Use the video compressor. Only need the sound? Try the MP4 to MP3 converter. For a short loop, use the video to GIF converter.
Features
- Converts MP4, MOV, WebM and MKV files
- Output as MP4 (H.264 + AAC) or WebM (VP9 + Opus)
- Fast copy without re-encoding when the codecs already fit
- High quality or Balanced preset when re-encoding is needed
- Preview the result and compare sizes before downloading
- Runs in your browser: the video is never uploaded
Frequently asked questions
How do I convert a video to MP4?
Drop the video on the page, keep MP4 selected and click Convert to MP4. If the video already uses H.264, it is copied into an MP4 in seconds without re-encoding.
Does converting a video lose quality?
Not when the codecs already fit the new format: the streams are copied and the picture is identical. When re-encoding is needed, the High quality preset keeps the result very close to the original.
Which formats can I convert?
MP4, MOV (QuickTime and iPhone videos), WebM and MKV as input. The output is MP4 with H.264 and AAC, or WebM with VP9 and Opus.
Is my video uploaded to a server?
No. The video is converted inside your browser using your device's media engine. It never leaves your computer or phone.
Should I choose MP4 or WebM?
MP4 plays almost everywhere: phones, TVs, social apps and editors. WebM is an open format that suits web pages and browsers. When unsure, choose MP4.
Which browsers are supported?
Recent Chrome, Edge and Safari on computers and phones. They provide the video encoders the tool needs. Firefox can copy videos but may not re-encode to H.264.