Convert to MP4

Yes. The video data is copied, not recomputed — a remux, not a transcode — so the output is bit-for-bit identical in picture quality to the source.

Advanced options cover trimming (start/end), downscaling, rotation, and audio removal. Rotation, end-only trimming, and audio removal copy the original stream untouched, so they stay lossless; downscaling and moving the start point require the video to be re-encoded, costing some quality and time. A badge tells you which case you are in before you convert.

Not reliably. It sometimes plays, but the internal structure still differs from the MP4 spec, so editors and upload validators often reject it. This tool rewrites the structure as a proper MP4.

Phone recordings and screen captures (H.264/HEVC video + AAC audio) convert losslessly almost every time. Production codecs such as ProRes or uncompressed PCM audio can also be copied across, but the resulting MP4 may not open in ordinary players — you are warned before converting.

Yes. If the video inside the MKV is H.264, HEVC, AV1 or VP9, it is copied across losslessly just like a MOV. If the audio is a format MP4 cannot hold (such as Vorbis), only the audio is re-encoded to AAC. Subtitle tracks inside the MKV (SRT, ASS) are not carried into the MP4, so keep a separate subtitle file if you need them.

The data is copied untouched, so the conversion itself is lossless. But a ProRes-in-MP4 file often will not play outside editing software. If your goal is normal playback or an upload form, re-encoding to H.264 with a desktop app is the better fit.

The input is read in pieces, so large files are fine to read. The finished MP4 is held in memory until you download it, so multi-gigabyte files can fail on low-memory devices.

Yes, the metadata tags from the source are carried over. Keep that in mind if the video contains location data and you are sharing it externally.