MKV to MP4

Re-encode an MKV file to MP4 with H.264 video and AAC audio so it plays on every phone, TV, and editor. We re-encode rather than remux because MKV files often contain codecs (HEVC, FLAC, subtitles) that MP4 doesn't carry the same way — re-encoding guarantees a clean, broadly compatible result. The conversion runs locally via ffmpeg.wasm, so your file never leaves your device. Performance depends on your CPU: expect roughly real-time encoding for short clips (a 5-minute 720p video may take 1–2 minutes). Very large files or 4K sources may be slow or run out of memory — for best results keep inputs under about 500 MB.