Are MP4 videos uploaded during conversion?
No. Video conversion runs locally on this device, so your file is not uploaded.
Local processing
MP4 to MKV Converter
Convert MP4 videos to MKV locally in your browser.
MKV is flexible and can sometimes be repacked quickly, but not every browser or social app can play it directly.
Select a video before converting.
Video is processed locally on this device with no upload. Recommended mode chooses the fastest compatible conversion path first.
Recommended. Tries the quickest no-recompress path first. If this file cannot use it, conversion continues automatically with a compatible method.
Related converters
MP4 WebM Convert MP4 videos to WebM locally in your browser. MP4 M4V Convert MP4 videos to M4V locally in your browser. MP4 MOV Convert MP4 videos to MOV locally in your browser. MP4 AVI Convert MP4 videos to AVI locally in your browser. MP4 MPEG Convert MP4 videos to MPEG locally in your browser. MP4 WMV Convert MP4 videos to WMV locally in your browser.
Questions
Why is MP4 to MKV slower than image conversion?
Video files are larger and may need to be re-packed or re-compressed before they work in the new format. MKV is flexible and can sometimes be repacked quickly, but not every browser or social app can play it directly.