Compress MKV Video Online
MKV files are popular for high-quality video storage but can be enormous. Compress them to compact MP4 files right in your browser.
Powered by ffmpeg.wasm - runs entirely in your browser
About MKV compression
MKV (Matroska) is a container that can hold losslessly encoded video. Re-encoding to H.264 with moderate quality settings can reduce file size by 50–80% while retaining good visual quality.
How to Get Started
Key Features
MKV supported
Handles MKV files including those with multiple audio tracks.
Audio preserved
Audio is re-encoded to AAC 128k for compatibility and smaller size.
No upload
Processing is 100% local. Your MKV never leaves your browser.
Compatible output
H.264 MP4 output plays everywhere: browsers, phones, TVs, apps.
Frequently Asked Questions
Can I compress a 4K MKV file?
Yes. You can also downscale it to 1080p or 720p using the resolution dropdown to dramatically reduce file size.
Will multiple audio tracks be kept?
The first audio track is re-encoded to AAC. Multiple tracks are not preserved in the MP4 output.
Is MKV better than MP4?
MKV supports more features but MP4 has better compatibility. For sharing, MP4 H.264 is the better choice.
How large of an MKV can I compress?
Files up to ~2GB work well on most desktop browsers. Larger files will work but may be slower.
Related
Ready to compress your MKV?
Go to the Video Compressor →