- Does converting MKV to MP4 lower the quality?
- Not for most files. MKV and MP4 are containers — they hold video and audio but don't decide how it's compressed. When the video inside is H.264, H.265, AV1, or VP9, this tool copies it into the MP4 bit for bit, the same way you'd move a file into a different folder. Audio in AAC, MP3, Dolby Digital, Opus, or FLAC is copied the same way. The only time anything is re-encoded is when MP4 players can't open a track: VP8 video becomes H.264, and Vorbis or uncompressed PCM audio becomes AAC. The plan shows you which case you're in before you click Convert.
- Why is it so much faster than other converters?
- Because re-encoding is the slow part, and most MKVs don't need it. Many converters decode every frame of the video and compress it again, which can take longer than the movie runs and loses a little quality each time. Copying tracks skips all of that — the work is reading the file and writing it back out. There's also no upload: a 3 GB file on a typical home connection takes 10 minutes or more to upload before an online converter even starts. Here it starts the moment you click.
- Is my video uploaded anywhere?
- No. The page reads the MKV from your disk in small pieces and builds the MP4 on your device. You can open your browser's network tab while it runs and watch — the video isn't sent to any server. That's also what makes large files practical: nothing has to travel over the internet, in either direction.
- What's the biggest file I can convert?
- In desktop Chrome and Edge, up to 64 GB — enough for a full Blu-ray rip. Those browsers can write the MP4 straight to a file on your disk, so the video is never held in memory. Other browsers, including Safari, Firefox, and every phone browser, have to build the MP4 in memory before offering the download, and holding a second copy of a large video can crash the tab, so the limit there is 2 GB. If your file is bigger, open this page in Chrome or Edge on a computer.
- What happens to subtitles and chapters?
- They stay behind in the MKV. MKV subtitles are usually SRT or ASS text tracks, and MP4 has no standard place for ASS styling, so most tools either drop them or convert them badly. If you need subtitles, keep the original MKV or save the subtitles as a separate .srt file next to the MP4 — VLC, Plex, and many TVs pick up a matching .srt automatically when it has the same name as the video.
- My MKV has several audio tracks. Which ones end up in the MP4?
- All of them that MP4 can carry, in the same order. MKVs often have a main language, a dub, and a commentary track; the MP4 keeps each one, and most players let you switch between them in the audio menu. Tracks in DTS or Dolby TrueHD are the exception. Browsers can't decode those formats, so they're left out, and the plan tells you which track numbers are affected before you convert.
- The MP4 plays without sound in my browser. What's wrong?
- Probably nothing with the file. Movies ripped from discs often carry Dolby Digital (AC-3) or Dolby Digital Plus audio, and some web browsers don't include a Dolby decoder, so they play the picture silently. Open the same MP4 in VLC, QuickTime, or on a TV and the sound is there. The tool shows a note when your file has Dolby audio so this doesn't catch you off guard.
- It says my MKV's video uses a format browsers can't read. What now?
- Older MKVs sometimes hold Xvid, DivX, MPEG-2, or VC-1 video, which no current browser can decode, so there's no way to convert them in a tab. Those files need a real re-encode, which a desktop video converter can do. The good news is that almost every MKV made in the last decade uses H.264 or H.265, which this tool copies without touching.
