A video converter that copies streams instead of re-encoding them
This free video converter changes the format of MP4, MOV, MKV, WebM and MPEG-TS videos right in your browser. Drop in one file or a whole batch, choose MP4, MOV, WebM or MKV, and each video is rewritten on your own device — nothing is uploaded, there is no watermark and no account. Download the results one by one or together as a ZIP.
Most converters decode every frame and compress it again, which is slow and always costs a little quality. Yet a video file is really a container wrapped around separate video and audio streams. When the new container can hold the streams you already have — H.264 moving from MOV to MP4, say — this tool simply copies them across. That is called remuxing: it is lossless, and even a long film takes seconds rather than minutes. Only a stream that truly has to change, such as VP9 going into MOV, is re-encoded with your browser’s hardware-accelerated encoders.
Before anything runs, every file lists its length, resolution, frame rate and codecs, with one line per track saying whether it will be copied or re-encoded, and why.
How to use the Video Converter
- Drop your videos on the upload area or click it to choose them. A mix of formats is fine.
- Under Convert to, pick MP4, MOV, WebM or MKV. The plan under each file updates at once: Copy means a lossless remux, Re-encode means that stream is compressed again.
- Leave Video codec and Audio codec on “Keep original” for the fastest result, or choose H.264, HEVC, AV1, VP9, AAC or Opus. Set Resolution to scale big videos down and Quality for anything re-encoded.
- Press Convert. A progress bar follows each file, and Cancel stops at any time.
- Compare the original and the result in the two preview players, then download each file or press Download all for a ZIP.
Video Converter features
Remux first, re-encode only when needed
Each track is checked against what the target format may hold. Compatible tracks are copied packet for packet, so quality and size stay the same.
Four formats, five video codecs
MP4, MOV, WebM and MKV, with H.264, HEVC, AV1, VP9 or VP8 video and AAC or Opus audio. Codecs your browser can’t encode are marked unavailable.
Every audio track kept
Films with several languages or a commentary keep all of them, in order, with their language labels.
An honest track report
Subtitle, timecode and camera-data tracks that can’t be carried over are named in the plan instead of vanishing silently.
Batch with ZIP download
Convert a folder of clips in one go; each file gets its own plan, status and download button.
Which format should you choose?
All four containers can hold excellent video. What differs is which devices and apps open them.
| Format | Best for | Plays on | Watch out for |
|---|---|---|---|
| MP4 | Sharing, phones, websites, editing, PowerPoint | Practically everything: iPhone, Android, Windows, Mac, smart TVs, browsers | H.264 + AAC gives the widest support |
| MOV | Apple workflows: Final Cut Pro, iMovie, QuickTime | Apple devices and most editors; Windows 10/11 and VLC play most files | Holds H.264, HEVC and ProRes here, not VP9 or AV1 |
| WebM | Web pages and HTML5 players | Chrome, Edge, Firefox, Android; Safari only in part | Needs VP8, VP9 or AV1 with Opus or Vorbis, so H.264 is re-encoded |
| MKV | Archives, multi-language films, media servers | VLC, Kodi, Plex, Android, many smart TVs, Windows 10/11 | Apple devices and most editing apps don’t open it |
Remux or re-encode: what actually happens
A remux reads the compressed packets from the old file and writes them, untouched, into a new container with fresh headers and a new index. Nothing is decoded, so the picture is bit-for-bit identical and the speed depends only on how fast your device reads the file. Turning an iPhone MOV into an MP4, or an MP4 into an MKV, is almost always a remux.
A re-encode decodes each frame and compresses it again. It happens when the target can’t store a codec (WebM can’t hold H.264), when you choose a different codec, or when you scale the picture down. The work is done by WebCodecs, the browser’s built-in encoders, which usually run on the graphics chip; 1080p often encodes faster than real time on a recent computer. To hit an exact file size instead, use the video compressor.
Formats, codecs and limits worth knowing
- Input: MP4, M4V, MOV, MKV, WebM and MPEG-TS (.ts, .mts, .m2ts). AVI and FLV need FFmpeg, which the AVI to MP4 and FLV to MP4 converters use.
- Dolby and DTS audio (AC-3, E-AC-3, DTS) can’t be decoded by browsers. MKV keeps them unchanged; for other formats you decide per track to keep them where allowed, leave them out, or convert them with ffmpeg.wasm — FFmpeg compiled to WebAssembly (GPL-2.0-or-later), a 32 MB download fetched only after you agree.
- Subtitles inside a file aren’t copied; save them first with Extract Subtitles.
- Rotation: MP4 and MOV keep a phone’s rotation flag. MKV and WebM have no such flag, so portrait clips are re-encoded upright.
- The engine is Mediabunny (MPL-2.0), loaded from a CDN the first time you add a video.
Video Converter FAQ
Is this video converter free and private?
Yes. There is no sign-up, watermark or file limit, and the conversion runs inside your browser: videos are read from your device and the results are created there. Only the converter’s code is downloaded.
Why did my video convert in a few seconds?
Its streams were copied rather than re-encoded. When the new format accepts the existing codecs, the tool only rewraps them — the quality is identical and the work is mostly reading and writing the file.
Does converting reduce quality?
Copied tracks lose nothing. Re-encoded tracks are compressed again, which always discards a little detail; the High and Very high settings keep that loss hard to see.
Which format plays everywhere?
MP4 with H.264 video and AAC audio. Choose MP4, then pick H.264 and AAC if your source uses something less common such as VP9, AV1 or Opus.
Why are HEVC or AV1 marked unavailable?
Your browser has no encoder for them on this device. Encoder support depends on the browser and the graphics hardware; H.264 and VP9 are available almost everywhere.
What happens to subtitles?
The browser engine reads video and audio tracks but not subtitle tracks, so they are listed and left out. Extract them first, then add them to the new file with Add Subtitles to Video.