How to use Video Converter
- 1Drop in a video file of any common format
- 2Choose the output container: MP4, WebM or MOV
- 3Pick a quality level — High, Balanced or Smallest file
- 4Convert, and watch the real ffmpeg progress
- 5Download the converted video
What Video Converter does
People say "video format" for two different things. The container — MP4, WebM, MOV — is the wrapper that holds streams and describes how they fit together. The codec is how the picture itself is compressed. A file can be an MP4 and still refuse to play, because the codec inside it is one the player does not know.
Converting therefore means decoding the existing streams and re-encoding them with a codec the target container expects. That is genuine work, unlike remuxing, and it is why conversion takes minutes where trimming takes seconds. It also means every conversion from a compressed source adds a generation of loss.
When to use it
- A file that will not play
- Older players and editing software support a narrow set of codecs. Converting to MP4 with H.264 is the most reliable route to a file that simply opens.
- Video for a web page
- WebM is the open-format option and every current browser plays it. MP4 remains the safest single choice if you can only ship one file.
- Footage for editing software
- MOV is what many editors prefer as an input. Converting first avoids the editor transcoding on import at settings you did not choose.
- Standardising a mixed set of clips
- Recordings from several devices in several formats become one consistent format, which matters before joining them in an editor.
Video Converter settings explained
- MP4
- H.264 video and AAC audio. The most compatible combination there is — it plays on every browser, phone, TV and editor in current use. Choose this unless you have a specific reason not to.
- WebM
- VP8 video and Vorbis audio. An open format with no licensing questions, supported by every current browser. Encodes more slowly than H.264 and produces somewhat larger files at the same quality.
- MOV
- Also H.264 and AAC, in Apple's QuickTime container. Preferred as an input by several editors; otherwise functionally similar to MP4.
- Quality level
- High (CRF 22), Balanced (CRF 27) or Smallest file (CRF 32). CRF is a quality target rather than a size target — the encoder spends whatever bitrate the footage needs to hit it, so the output size depends on your content.
- Why WebM uses VP8, not VP9
- VP9 would give better compression, but the single-threaded WebAssembly encoder reliably crashes inside it with a memory fault. VP8 is what this engine handles dependably, and every browser plays it. A working file beats a slightly smaller one that never finishes encoding.
The three output formats
| Format | Video codec | Audio codec | Best for |
|---|---|---|---|
| MP4 | H.264 | AAC | Maximum compatibility |
| WebM | VP8 | Vorbis | Open-format web delivery |
| MOV | H.264 | AAC | Editing software input |
Limits and what to expect
- Converting from a compressed source always adds a generation of loss, whatever quality level you pick.
- WebM output is VP8 rather than VP9, so files are larger than a VP9 encode would be.
- Encoding is single-threaded, because the multi-threaded build needs cross-origin isolation the site does not use.
- Resolution and frame rate are preserved — this tool changes format, not dimensions.
- The first run downloads a ~32 MB engine, which is then cached.
Troubleshooting
- WebM conversion is much slower than MP4
- VP8 encoding is inherently slower than H.264, and both run single-threaded here. If you do not specifically need an open format, MP4 will finish sooner and produce a smaller file.
- The converted file is larger than the original
- The source was encoded more efficiently than your chosen quality level, or with a newer codec such as H.265 or VP9. Re-encoding to H.264 or VP8 cannot match that, so the file grows. Choose Smallest file, or leave the video in its original format.
- It is taking a very long time
- Every frame is decoded and re-encoded on one thread in your browser. A long or high-resolution video is genuinely slow. Trim to the section you need first — that is a stream copy and costs almost nothing.
- The browser ran out of memory
- Both the source and the output are held in the tab. Close other tabs, or split the video and convert the parts separately. Long 4K files are the usual cause.
Your files and your privacy
Conversion runs through an ffmpeg build compiled to WebAssembly, executing in your browser on your own device. No frame is uploaded and nothing is queued on a server. The only network request is for the engine, which is generic code shared by every visitor and contains nothing of yours.
What to use next
FAQ
What is the difference between a container and a codec?
The container — MP4, WebM, MOV — is the wrapper holding the streams and describing how they fit together. The codec is how the picture is compressed inside it. A file can have the right container and still not play, because the codec inside is one the player does not support.
Which format should I choose?
MP4 unless you have a specific reason otherwise — H.264 and AAC play on essentially everything. WebM if you need an open format for the web. MOV if the file is going into editing software that prefers it.
Why is WebM encoded with VP8 rather than VP9?
VP9 compresses better, but the single-threaded WebAssembly encoder reliably crashes inside it with a memory access fault. VP8 is what this engine handles dependably and every current browser plays it. A file that encodes successfully is worth more than a slightly smaller one that never completes.
Does converting reduce quality?
Yes. The source is decoded and re-encoded, and since it was almost certainly already compressed, the output is a second generation. Choosing High quality limits how much is lost, but no conversion can improve on the source.
Can I change the resolution while converting?
Not here — this tool changes format and keeps the dimensions. Use the video resizer for that, which scales and re-encodes in one pass.
Is my video uploaded to a server?
No. Encoding happens inside your browser using WebAssembly, and the tool works with the network disconnected once the engine has loaded.