Free online H265 to MKV converter

What the H.265 format is

H.265, also called HEVC, is a video codec rather than a container. It compresses video more efficiently than H.264, so cameras, screen recorders, smartphones, Blu-ray sources, and streaming tools use it for high-resolution video at reduced file sizes.

H.265 video commonly appears in .h265, .hevc, .mp4, .mov, and .mkv files. The filename extension does not prove which codec is inside a container. Use FFmpeg's ffprobe to check:

ffprobe -v error -select_streams v:0 -show_entries stream=codec_name -of default=nw=1 input.mp4

What the MKV format is

MKV, or Matroska Video, is a multimedia container that can hold video, multiple audio tracks, subtitles, chapters, attachments, and metadata in one file. It can contain H.265 video without changing the video codec.

MKV is useful for long-term storage, downloaded video, multilingual releases, subtitle-heavy files, and home media servers. Its broad stream support is an advantage when an MP4 or MOV file cannot retain every audio, subtitle, or chapter track.

How to convert H.265 to MKV

Remux an existing container with FFmpeg

Install FFmpeg, open a terminal in the folder containing the source, and run:

ffmpeg -i input.mp4 -map 0 -c copy output.mkv

-map 0 includes all detected streams, while -c copy copies them without re-encoding. Replace input.mp4 with the actual source filename; the source can also be .mov or another container.

Put a raw H.265 stream into MKV

A raw .h265 or .hevc file normally contains video only. Create the MKV container with:

ffmpeg -f hevc -i input.h265 -c:v copy output.mkv

This produces an MKV with no audio or subtitles because a raw H.265 stream does not contain those tracks. If separate audio exists, add it explicitly:

ffmpeg -f hevc -i input.h265 -i audio.aac -map 0:v:0 -map 1:a:0 -c:v copy -c:a copy output.mkv

Use MKVToolNix without re-encoding

In MKVToolNix GUI, choose Multiplexer → Add source files, select the video, confirm the desired audio and subtitle tracks, set the destination filename to output.mkv, and choose Start multiplexing. This is a container operation, so it is fast and does not reduce image quality.

Convert on 101convert.com

You can convert the file on 101convert.com for free without installing software. Upload the source, select MKV as the output format, start the conversion, and download the resulting file. Avoid uploading confidential or copyrighted material unless the service and your permissions allow it.

Quality, compatibility, and limitations

Remuxing preserves the original H.265 bitstream, resolution, frame rate, and quality. It also does not make H.265 playable on a device that lacks H.265 decoding; it changes the container only.

If the target device supports MKV but not H.265, re-encode the video to H.264:

ffmpeg -i input.mp4 -map 0 -c:v libx264 -crf 20 -preset medium -c:a copy output.mkv

This takes substantially longer, increases or decreases the file size depending on the source settings, and introduces generation loss. Some devices also reject specific H.265 profiles, 10-bit video, high frame rates, or audio codecs even when they accept MKV; inspect those stream properties before troubleshooting the container.