Question 1

Which formats can I convert between?

Accepted Answer

MP4, MKV, MOV, WebM and AVI. MP4, MKV and MOV use H.264 video with AAC audio; WebM uses VP8 with Vorbis; AVI uses MPEG-4 with MP3. Pick the target format and a quality level, and it’s converted right in your browser.

Question 2

Are my videos uploaded anywhere?

Accepted Answer

No. Conversion happens entirely on your device — your video is never uploaded. The only network request is a one-time download of the media engine (about 32 MB), which is then cached. Your video itself always stays local, so the tool is on-device but not “fully offline”.

Question 3

Why can’t I preview some converted formats?

Accepted Answer

Browsers can play MP4, WebM and usually MOV inline, but most can’t play MKV or AVI. When that happens we show a note instead of a broken player — just download the file and it’ll open in your usual media player.

Question 4

Why is WebM so much slower?

Accepted Answer

WebM uses the VP8 video codec, which is heavier to encode in the browser than H.264. It still works and stays entirely on your device — it just takes longer, so it’s best for short clips. You can cancel at any time.

Question 5

How long does it take, and is there a size limit?

Accepted Answer

There’s no hard limit, but in-browser conversion is single-threaded and slow, so short clips (under ~1–2 minutes or ~50 MB) are the sweet spot. Larger or longer videos work but can take 15+ minutes and a lot of memory, and WebM is the slowest. We warn you, sized to your file, before you start, and show elapsed time plus a rough estimate while it runs, with a Cancel button. It’s completely free, with no sign-up and no watermark.

Video Converter

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Video Compressor

MP4 to MP3