Online Video Converter

This multi-format video converter uses FFmpeg WebAssembly to transcode videos directly in the browser without any server upload. The tool loads the FFmpeg core (approximately 31MB) from a CDN as a WebAssembly module, providing native-speed encoding and decoding capabilities entirely client-side.

The converter accepts seven input formats (MP4, AVI, MOV, MKV, WebM, FLV, WMV) and produces five output formats. For MP4, AVI, MKV, and MOV outputs, the tool uses the H.264 (libx264) video encoder with the 'fast' preset and CRF 23 for an excellent quality-to-speed balance, paired with AAC audio at 192 kbps. MOV outputs additionally include the +faststart flag for web streaming compatibility. WebM outputs use the VP8 (libvpx) video encoder with CRF 30 and variable bitrate, paired with Vorbis audio at quality level 5.

The uploaded video file is written to FFmpeg's virtual in-memory filesystem. FFmpeg's progress callback events drive the percentage bar in real-time as frames are processed. The output file is read back from the virtual filesystem, packaged as a Blob with the appropriate MIME type, and offered for download. The entire pipeline runs within a Web Worker thread, keeping the main UI responsive during conversion.