Video Converter
Convert a video your browser can play into MP4 or WebM - nothing uploaded.
Your video is processed inside this page and never uploaded.
This works by playing the video into a recorder, so it takes about as long as the video itself (a 2x speed-up takes half as long). Keep this tab in front while it runs. The result is re-encoded as WebM, or MP4 where your browser can write it.
What this tool does
A video converter re-saves a video in a different format. This one plays any video your browser can open - MP4, WebM, many MOV files - and records it again as MP4 or WebM using the browser’s own encoder. It is limited to formats your browser can both play and write.
Plays the source into a recorder and saves it as MP4 (H.264) or WebM (VP9 or VP8), at a quality you choose.
Tells you if your browser cannot write the chosen format, so you can pick the other.
How to use it
- Choose your video.
- Choose MP4 or WebM as the target.
- Choose a quality level.
- Press Start and wait - it runs in real time.
- Check the result and press Download video.
Why use this video converter
Converts between MP4 and WebM using your browser’s own encoders, and tells you plainly when your browser cannot write the format you asked for. Different devices, editors and websites accept different video formats, and a WebM from a screen recorder or a MOV from a phone will not always be taken. Converting to MP4 is the usual way to get a file that works almost everywhere.
Why we built it
We built the video converter to use your browser's own encoders and to say plainly when your browser cannot write a format. Reduce the size with compress video and extract sound with video to MP3.
Who this tool is for
- People whose device or site wants MP4 or WebM
- Creators preparing uploads
- Teachers sharing recordings
When to use it
- A site or editor will not accept your video’s format.
- You need an MP4 from a WebM screen recording.
- Making a WebM version for the web.
- Standardising a mix of clips into one format.
How it works
The browser decodes the source, as it would to play it, and the page records that playback with MediaRecorder using an MP4 or WebM encoder. Both the container and the video and audio codecs are new.
Which formats can be written depends on the browser: current Chrome and Edge can write MP4 with H.264, and every major browser can write WebM. Formats the browser cannot play at all - some MKV or AVI files - cannot be converted here.
This is a re-encode in real time, not the fast stream-copy that desktop converters can do when only the container changes.
This tool plays the video into a recorder, so processing takes about as long as the video itself and the tab must stay in front. The result is re-encoded, so it is a new generation of the video rather than a lossless cut.
What you give it, and what you get back
| Item | Details |
|---|---|
| Input | A video your browser can play. |
| Target | MP4 or WebM. |
| Quality | Balanced, high or very high bitrate. |
| Output | A converted video file. |
Issues you may run into
| What you see | Why it happens | What to do |
|---|---|---|
| "Cannot write MP4" message | Your browser has no MP4 encoder for MediaRecorder. | Choose WebM, or use a recent Chrome or Edge. |
| File will not load | The browser cannot play that format. | Try an MP4, WebM or MOV file. |
| Result is larger | The bitrate is higher than the source’s. | Choose a lower quality setting. |
| It takes a long time | Processing is real time. | Convert a shorter clip. |
Assumptions and limitations
- Runs in real time, so a long video takes a long time.
- The tab must stay in the foreground, because browsers throttle background tabs.
- The result is re-encoded as WebM, or MP4 where your browser can write it - it is not a lossless edit.
- Very large files depend on your device’s memory and the formats your browser can play.
Frequently asked questions
How do I convert a video to MP4?
Choose the video, pick MP4 as the target, and press Start. The converted video can be downloaded when it finishes.
Can I convert MOV to MP4?
Yes, if your browser can play the MOV file. Many MOV files from phones use H.264 and play fine.
Why can it not write MP4 in my browser?
MP4 recording is only available in some browsers. Use a recent Chrome or Edge, or choose WebM.
Is my video uploaded?
No. It is converted in your browser and saved to your Downloads folder.
Why does conversion take as long as the video?
The browser records the video as it plays, so processing is in real time.