HEIC to JPG: Quality, Metadata, and Privacy
A careful HEIC-to-JPG workflow preserves the picture you need without accidentally sharing location data or repeatedly degrading the image.
Read guide →Convert Video
Convert between MP4 with H.264 and WebM with VP9 in your browser, with no queue and no server-imposed file size cap.
Drop a video here or click to browse
MP4, WebM, MOV, AVI — processed locally and never uploaded.
Reviewed 2026-08-15
Free Convert Video – how it works
Two output targets are available. MP4 uses libx264 for video and AAC for audio, which is the combination that plays on essentially every device and editor made in the last decade. WebM uses libvpx-vp9 with Opus audio, which usually reaches the same visual quality at a smaller size and is a good fit for embedding video on a web page.
MP4 output is encoded at CRF 22 and WebM at CRF 30 in constant quality mode. The numbers are not comparable across codecs; both are tuned to land near visually transparent for typical footage.
VP9 encoding is considerably slower than H.264, especially in a browser where FFmpeg runs single threaded. Converting to WebM will take longer than converting to MP4 for the same input, so budget for that on anything but a very short clip.
How to use Convert Video online
- Add the source video. Drop in MP4, WebM, MOV, AVI, or MKV. The container matters less than the codecs inside it, and FFmpeg reads all of these directly.
- Choose MP4 or WebM. Pick MP4 for maximum compatibility, sharing, and editing. Pick WebM when you are putting the video on a website and want the smallest file that modern browsers can play.
- Convert and check playback. Run the conversion and play the first few seconds of the result. Confirm the audio survived if the source had a sound track.
When to use it
- Turn a MOV from an iPhone into MP4 so Windows and older editors will open it.
- Produce a WebM version of a clip to cut page weight on a site.
- Rewrap an MKV download into MP4 for a device that refuses to play it.
- Standardise a folder of mixed formats before importing them into one project.
Known limitations
- Everything is bounded by the memory one browser tab can claim. Clips under about 30 seconds are comfortable; multi-minute or 4K footage often stalls or fails with an out-of-memory error.
- VP9 encoding is slow in WebAssembly. A clip that converts to MP4 in under a minute can take several times longer as WebM.
- Conversion re-encodes, so it is not lossless. If you only need a different container and the codecs are already right, a stream copy in a desktop tool preserves quality better.
Frequently asked questions
Should I choose MP4 or WebM?
MP4 if the file needs to play or be edited anywhere without thought. WebM if it is going on a web page and file size matters, since VP9 generally beats H.264 at the same quality.
Can I convert MOV files from my iPhone?
Yes. MOV inputs are read directly and can be written out as either MP4 or WebM. MP4 is the usual choice because it keeps H.264 compatibility while dropping the Apple-specific container.
Is my video uploaded to a server?
No. FFmpeg is compiled to WebAssembly and runs inside the page, so the file is read from your disk into the tab's own memory. Nothing about the video is sent to opentools.
Is there a file size limit?
No limit is imposed by a server, because there is no server involved. The practical ceiling is your device: the file has to fit in the browser tab's memory alongside the decoded frames FFmpeg is working on.
Why does the first render take longer?
The FFmpeg WebAssembly build is about 31 MB and has to download before the first job can start. The browser caches it afterwards, so later visits skip that step and begin encoding almost immediately.
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