Video Converter (MP4, WebM, MOV, MKV)

Convert videos between MP4, WebM, MOV and MKV right in your browser. Compatible codecs are remuxed instantly with zero quality loss — nothing is ever uploaded.

Convert MP4, WebM, MOV and MKV video free in your browser — no upload, no watermark. Compatible codecs are copied instantly with zero quality loss.

About Video Converter (MP4, WebM, MOV, MKV)

A video converter that changes a video's container format (MP4, WebM, MOV or MKV) entirely on your device using your browser's built-in WebCodecs engine. When the video and audio codecs already fit the target format, it remuxes — copying the packets 1:1 without re-encoding — so the conversion is near-instant and completely lossless.

How to use Video Converter (MP4, WebM, MOV, MKV)

  1. Drop a video into the tool — MP4, M4V, MOV, WebM, MKV and MPEG-TS files are read, up to 2 GB, and never leave your browser.
  2. Review the detected details: container, dimensions, duration, video codec, audio codec and frame rate.
  3. Pick the output format — MP4, WebM, MOV or MKV. A note tells you whether your codecs will be copied as-is (instant, zero quality loss) or need re-encoding.
  4. Optionally open Advanced options to downscale to 1080p or 720p, set a target video bitrate in Mbps, or force a full re-encode.
  5. Click Convert and watch the progress bar — you can cancel at any time.
  6. Preview the result, compare the original and converted sizes, and save the new file.

Frequently asked questions

Is my video uploaded to a server?
No. The whole conversion runs inside your browser using WebCodecs — the file is read from your device, converted on your device, and saved back to your device. Nothing is uploaded, so even multi-gigabyte videos stay private.
What is remuxing, and why was my conversion instant?
Formats like MP4, MOV and MKV are just containers around compressed video and audio streams. When your streams are already allowed in the target container, the tool remuxes: it copies the compressed packets 1:1 into the new wrapper without decoding a single frame. That is why converting an H.264 MOV to MP4 takes seconds and loses zero quality.
Which output format should I choose?
MP4 is the safest all-round choice — it plays everywhere, from phones and TVs to editing apps and websites. WebM is best for the open web (it requires VP8/VP9/AV1 video, so other codecs get re-encoded). MKV is a flexible container for archiving almost any codec, and MOV is the native choice for Apple and pro-video workflows.
Will converting reduce my video's quality?
Not if it can be remuxed — a packet copy is bit-for-bit lossless. Quality is only touched when a re-encode is required: either the codecs are not allowed in the target format (for example H.264 into WebM), or you deliberately change resolution or bitrate in Advanced options, or you toggle Force re-encode.
Can I convert iPhone (HEVC/H.265) MOV videos to MP4?
Yes. HEVC is a permitted codec inside MP4, so iPhone MOV recordings usually remux to MP4 instantly with no quality loss. Note that the result is still HEVC video — if a device cannot play HEVC at all, use Force re-encode so the video is re-encoded to a more widely supported codec.