Video Converter
Converts WEBM, MOV, MKV and AVI to MP4, or the other way round. It uses FFmpeg running in the browser; the engine (about 31 MB) downloads once.
Conversion time and size limits depend on your device and codec. Test a short file first. Non-GIF conversions never silently discard audio to recover from an encoding failure.
Output formats and quality settings
These numbers come from converting the same 10-second 1280×720 30 fps clip (9,796.5 KiB as WEBM) with this tool. A lower CRF means higher quality; times are from a PC.
| Output | Codecs | Size | Time | Use |
|---|---|---|---|---|
| MP4 (CRF 28) | H.264 + AAC | 737.3 KiB | 15.6 s | Tight attachment limits |
| MP4 (CRF 23, standard) | H.264 + AAC | 1,541.9 KiB | 17.1 s | Messaging, social media, YouTube |
| MP4 (CRF 18) | H.264 + AAC | 4,027.3 KiB | 19.9 s | Intermediate file for more editing |
| WEBM | VP8 + Vorbis | 2,288.3 KiB | 12.4 s | Embedding in a web page |
| MOV | H.264 + AAC | 1,542.0 KiB | 16.9 s | Same content as MP4, different container |
| GIF | 256 colours, 12 fps, 480 px wide | 8,864.1 KiB | 10.2 s | Forums that do not accept video |
Even shrunk to 480 px and stripped of sound, the GIF was 5.7 times the size of the standard MP4, because GIF stores every frame as a whole 256-colour picture. When you need a short loop, a silent MP4 usually wins on both quality and size.
How to use
- Drop a video into the window or click to browse. On your first visit the engine downloads first, and it is worth testing with a short file.
- Choose the quality (CRF 28, 23 or 18) at the top, set the output format on each card and press Convert. With several files, “Convert all” processes them in order.
- When it finishes, compare the original and the result: duration, orientation, sound at the start and end, and lip sync. Then download.
GIF and file-size tips
- Keep GIFs short: size scales almost linearly with length. Trimming to 3–5 seconds keeps it to a few megabytes, while a whole clip turns into tens of megabytes.
- Width and frame rate: GIFs here are fixed at 480 px wide and 12 frames per second, a balance between quality and size. If you need something larger, upload an MP4 and let the page scale it.
- Low-motion scenes: a screen recording with a static background compresses fairly well as GIF. Shaky footage or frequent cuts force every frame to be stored again and the file grows quickly.
- Order of savings: trim what you do not need, then raise CRF to 28, and only then reduce the resolution. Moving from CRF 18 to 28 made the same clip 5.5 times smaller.
- Screen-recorded WEBM: browser recordings have irregular frame timing. This tool keeps the source timing, so if a conversion takes unusually long, reload the page to make sure you have the latest version.
Frequently asked questions
Do the frame rate and resolution change?
MP4, WEBM, MOV, MKV and AVI keep the source resolution and frame rate. Our 10-second 30 fps clip came out with the same length and resolution. GIF is the exception: it is reduced to 480 px wide at 12 frames per second with no sound. Screen recordings with irregular frame timing are converted while preserving the original timestamps.
How long does conversion take?
On a PC, a 10-second 1280×720 clip took roughly 9–20 seconds depending on the format. Time scales with length and resolution, and a lower CRF (higher quality) takes a little longer. Files are processed one at a time in the browser, so a one-minute video takes one to two minutes and a ten-minute video much longer. A progress bar runs meanwhile and you can queue other files.
Can it handle long or large videos?
There is no fixed limit, but browser memory is the practical ceiling: input, output and working space all live in RAM, so even fairly short videos can fail on a phone. Use a computer, split the video, or lower the resolution and try again. If it fails you get an error message and your file is left untouched.
Are subtitles and multiple audio tracks preserved?
No. This tool creates copies for sharing and playback; subtitle tracks, multiple audio tracks, HDR colour information and capture metadata are not preserved. Keep your original for archiving and use the converted file for upload or playback. A successful conversion also does not guarantee playback in every app, so open the result where you plan to use it.