video tool
MP4 to WEBM
Transcode MP4 to WebM (VP8 + Opus when an audio track is present; resolution/fps capped for ffmpeg.wasm memory) locally with ffmpeg.wasm.
How it works
- Convert MP4 (H.264 + AAC) to WebM (VP8 + Opus) in the browser; high-resolution sources use a stricter scale cap so short HD clips are less likely to hit wasm memory limits.
FAQ
- Are my files uploaded to your servers?
- No. By default, Awesome Tools processes files entirely in your browser. Nothing is sent to our servers for conversion.
- Why is it slow the first time?
- ffmpeg WebAssembly is downloaded on demand. Subsequent runs may be faster due to caching.
- Why does conversion fail with “memory access out of bounds” or similar?
- That error is usually wasm running out of heap, not a “length bug”: the browser still decodes your MP4 at full resolution before scaling, and VP9 plus Opus together can exceed limits even for a 1s 1080p clip. This tool uses VP8 + Opus and tightens the scale target on high-resolution sources; very heavy files may still need desktop ffmpeg.
- Why did my conversion fail?
- Large files, unusual codecs, or browser memory limits can cause failures. Try a smaller file or a different browser. See the limits on this page.