How to convert MKV to MP4
- Drop one .mkv file. MP4, MOV, WebM and photos are refused here.
- Press “Convert to MP4”.
- Download the MP4 and play it once before you delete the original.
The first visit loads FFmpeg into this tab. Later visits reuse the browser cache. Many MKV files already hold H.264 and AAC, so GustKit can remux them into an MP4 with faststart in seconds.
Remux first, encode when the codec does not fit
When the streams already match what MP4 players expect, GustKit copies them into a new file. Odd video or audio codecs trigger a fallback encode to H.264, yuv420p and AAC at 128 kbps.
MOV to MP4 is the QuickTime sibling. Compress video shrinks the MP4 after you convert. Trim video cuts a long file first.
The MKV stays in this tab
GustKit does not fetch a file from a link. Close the tab and the clip is gone from memory. The free size bar shows 1024 MB for this tool.
How to check the MP4 before you send it
- Play the download and watch one scene with dialogue if the MKV had speech.
- Compare the file size with the original.
- Keep the MKV until the MP4 opens everywhere you need.
MKV files from anime rips or screen recorders vary widely. Remux is fast when the codecs already match MP4. Nothing is uploaded.