Convert video to WebM
Convert a clip to VP9 WebM for the open web. Files stay on your device.
How this works locally
- You choose a file; the page reads it from your device.
- The matching engine is loaded from fileslimmer.com and runs in a Web Worker.
- The result is written back to a location you choose on this device.
Before or choose files from your device
Original size —
Accepted formats
- Reads
- MP4 · MOV · M4V · WebM
- Writes
- WebM
Estimated memory
Your browser reports only a coarse memory hint, so this figure is an estimate.
| Device profile | Largest video | Longest clip | Multi-threaded fallback |
|---|---|---|---|
| Minimal | 50 MiB | 5 minutes | Single thread |
| Low | 120 MiB | 15 minutes | Single thread |
| Balanced | 300 MiB | 45 minutes | When isolated |
| High | 700 MiB | 120 minutes | When isolated |
Your browser is placed in one of these profiles from the coarse hints it exposes. A file above the limit is refused before it is read, rather than after the tab has run out of memory. On an iPhone or iPad a further ceiling applies whatever the profile — largest video: 50 MiB, longest clip: 5 minutes, multi-threaded fallback: Single thread — because mobile Safari reclaims a tab's memory far more abruptly than the hints can predict.
Limitations
- Re-encoding always costs some quality, and which codecs are available is decided by your browser, not by this page. A clip above the device limit is refused before it can exhaust the tab.
- Every frame is decoded and encoded again. On a phone that is the most demanding thing this site can ask of the device, and the browser may throttle it part-way through.
- VP9 encoding takes noticeably longer than H.264 for the same clip and the same quality target.