Video format converter: convert to MP4 or WebM online
Choose a video and the format to save it as, and press Convert. The converted copy is made in your browser.
Free · no signup Runs in your browser
How do I convert a video to MP4 or WebM?
Choose your video, pick MP4 or WebM in Save as, set the quality and, if you like, a smaller height, and press Convert the video. The tool plays the video and records it in the new format with your browser's own encoder, so it takes about as long as the video. Recent Chrome, Edge and Safari can record MP4; Firefox records WebM only. Your video is never uploaded.
Why we built this tool
Video formats are a regular source of frustration: a WebM from a screen recorder that your phone or an editing app will not open, a MOV from an iPhone that a form rejects, an MP4 that a website wants as WebM. Desktop converters can do all of it but need installing; most online converters upload your video to a server and send it back. This tool converts in your browser with the encoder your browser already has, which is limited to the formats the browser can record but keeps the video on your device.
Your video is processed in your browser. Nothing is uploaded, and there is no watermark.
How it works in detail
A file format has two parts: a container (MP4, WebM, MOV) that holds the streams, and codecs (H.264, VP9, AAC, Opus) that compress the picture and the sound. A browser can play whatever its codecs allow, and record to the formats its recorder supports, which typically is WebM with VP8 or VP9 and Opus, and, in recent Chrome, Edge and Safari, MP4 with H.264 and AAC. This tool plays your video, redraws each frame on a canvas and records it into the format you choose. It therefore can convert anything your browser can play (including many MOV and MKV files with H.264) into WebM, and into MP4 where the browser can record MP4. It cannot create formats the browser cannot record, such as AVI, WMV or FLV, and it does not copy streams without re-encoding.
How to use it
- Choose your video. If it will not play in the preview, your browser cannot read it.
- In Save as, choose MP4 (if offered) or WebM.
- Choose the quality and, if needed, a smaller height or a lower frame rate.
- Press Convert the video and keep the tab open until it finishes.
- Check the result and download it.
Which format should I pick?
A short guide to the two formats on this page.
| Format | Plays in | Best for |
|---|---|---|
| MP4 (H.264 and AAC) | Almost everything: phones, TVs, Windows, Mac, social media, editors | Sharing, uploading, email, editing |
| WebM (VP8/VP9 and Opus) | Chrome, Edge, Firefox, Android, VLC; some Apple devices and older apps cannot | Websites, screen recordings, small files |
Use cases
- Making a WebM screen recording playable in an editor or on a phone
- Converting a MOV or MKV from a camera into a file a website accepts
- Making a WebM version for a web page
- Shrinking a video while converting it
- Preparing a video for a form that wants MP4
- Testing how a clip looks in another format
Problems you may run into
Most trouble is about what the browser can read and write.
| What you see | Likely cause | What to do |
|---|---|---|
| It says it cannot read my video | The browser cannot play that codec (for example HEVC/H.265 in some browsers, or a camera's special format) | Try Chrome, Edge or Safari, or convert the file to H.264 MP4 first |
| It takes as long as the video | The video is recorded as it plays; there is no shortcut in a browser | Use a shorter clip, or start it and leave the tab in front while you do something else |
| The output stops or the picture freezes | The tab was hidden, the computer went to sleep, or it ran out of power | Keep the tab open and visible, plug in a laptop, and run it again |
| There is no sound in the result | The sound option was off, the video has no sound, or the browser blocked audio until you clicked | Check the box is off, press the button yourself, and try again |
| The quality is a little lower than the original | The video is decoded and encoded again, which always costs some quality | Choose High or Very high quality, and keep your original file |
| The file is WebM and my app wants MP4 | Most browsers can only record WebM | Choose MP4 where your browser offers it (recent Chrome, Edge, Safari), or convert the file afterwards |
| MP4 is greyed out in Save as | This browser cannot record MP4 (Firefox, for example) | Use Chrome, Edge or Safari, or convert to WebM here and then use an MP4 converter |
| My AVI, WMV or FLV file will not open | Browsers cannot play those formats | Use a desktop converter such as HandBrake or VLC |
Privacy and rights
The video stays on your device. Conversion does not change who owns the video or who may share it.
How it works
The video is played, redrawn and recorded again in your browser.
1. The video is opened in a hidden player in your browser; nothing is uploaded.2. The player runs from the start point while each frame is drawn on a canvas (turned, resized or mirrored if you asked).3. The browser's MediaRecorder records the canvas and the sound as a new video.4. When the end point is reached the file is finished and offered as a download.
This uses the browser's own encoder, so the output is WebM (VP8/VP9) or, in browsers that can record it, MP4 (H.264). It is a new encoding, not a lossless cut, so there is a small quality cost, and the work takes about as long as the part you choose. The tab must stay open and visible. Very long videos (over about an hour) may exhaust memory; cut them into parts first. Files protected by copy protection (DRM) cannot be processed.
Example: a WebM screen recording as MP4
A 4-minute WebM screen recording will not open in a colleague's app.
- Save asMP4
- QualityStandard (2.5 Mbps)
- Timeabout 4 minutes; about 75 MB
An MP4 that opens almost everywhere
In Firefox, convert in Chrome or Edge instead.
Terms on this page
- Container
- The file format (such as MP4 or WebM) that holds the picture and sound streams.
- Codec
- The method used to compress the picture or sound, such as H.264 or Opus.
Common questions
Is it free, and is my video uploaded?
It is free, and your video is processed in your browser and never uploaded.
Which formats can I convert to?
WebM, and MP4 in browsers that can record it (recent Chrome, Edge and Safari).
Which formats can I convert from?
Any video your browser can play, such as MP4, MOV (H.264), WebM and some MKV files.
Is it as good as a desktop converter?
It re-encodes, so there is a small quality cost, and it works in real time. A desktop converter is faster for long videos.
Why can I not pick MP4?
Your browser cannot record MP4. Try Chrome, Edge or Safari.
Is anything I enter sent to a server?
No. The calculation happens in your browser and nothing you type leaves your device.
Where these numbers come from
- MDN Web Docs — MediaRecorder How a browser records a stream, and isTypeSupported() for choosing a format.
- MDN Web Docs — HTMLCanvasElement.captureStream() How frames drawn on a canvas become a video stream that can be recorded.
- Wikipedia — Video file format Containers (MP4, WebM) and codecs (H.264, VP9) and how they differ.
Last verified 2026-10-25 The method on this page is checked against the sources above at least once a year. Spotted something out of date? Tell us and we will fix it.
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