Convert RAR to MKV

A downloaded movie may arrive as a multipart RAR archive even though a television, media server, or editor requires an MKV file. Usually the task is to extract the original video, then remux or transcode it only when its existing format is unsuitable.

What the RAR format is

RAR is a compressed archive format developed by Eugene Roshal and commonly created with WinRAR or other RAR-compatible archivers. It can store one or more files, split a large archive into parts such as movie.part1.rar and movie.part2.rar, and include password protection or recovery records. 7-Zip can extract RAR archives but cannot create them.

For a multipart archive, put every part in one folder and open or extract only the first part, usually filename.part1.rar. Older sets may use filename.rar, filename.r00, filename.r01. A missing part, wrong password, or damaged archive prevents complete extraction.

What the MKV format is

MKV, or Matroska Video, is a container, not a video codec. It can hold video, multiple audio tracks, subtitles, chapters, attachments, and metadata in one file. Common contents include H.264, H.265/HEVC, VP9, or AV1 video and AAC, AC-3, DTS, or Opus audio.

MKV is useful when a media server, player, editor, or archive workflow supports Matroska and needs several tracks or subtitle streams. It does not inherently compress video or make a file smaller; size depends on the encoded streams and their bit rates.

Extract an MKV that is already in the archive

1. Install 7-Zip or WinRAR from its official download source.
2. Right-click the first archive part and choose 7-Zip → Extract to “filename\”, or use the equivalent WinRAR extraction command. Enter the password if requested.
3. Open the destination folder and locate the extracted .mkv file. Extraction restores the original file; it does not convert or reduce its quality.

From a terminal, 7-Zip can extract a multipart set with:

7z x filename.part1.rar -ooutput_folder

Do not rename .rar to .mkv; changing the extension does not change the file format.

Remux another video into an MKV container

If extraction produces MP4, AVI, MOV, or another video format, use FFmpeg for a local conversion. When the codecs are suitable for Matroska and the target device, stream-copying changes the container without re-encoding:

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

-map 0 includes all input streams that FFmpeg can map, including audio, subtitles, chapters, and attachments. Stream copying is fast and does not reduce quality, but it can fail when a stream or codec is incompatible with the MKV container or the target device.

MKVToolNix GUI provides a graphical alternative for remuxing. Open MKVToolNix GUI → Multiplexer, add the extracted file, select tracks, configure track language and default flags, then start multiplexing. It can adjust tracks, subtitles, chapters, and metadata without re-encoding compatible streams.

Transcode incompatible streams

Use transcoding when the target device rejects the source codec or when remuxing fails. This example encodes the first video stream as H.264 and the first available audio stream as AAC:

ffmpeg -i input.avi -map 0:v:0 -map 0:a? -c:v libx264 -crf 18 -preset medium -c:a aac -b:a 192k output.mkv

Transcoding decodes and re-encodes the media, so it takes longer, may reduce quality, and can change the file size. Lower CRF values generally produce larger H.264 files with higher quality; test the result on the intended device rather than repeatedly changing the extension.

Use an online converter only for suitable files

Services such as CloudConvert and Convertio can convert many common video files to MKV, subject to current codec, size, and account limits. Extract the video locally first and upload that file rather than the RAR archive, because online services may not support multipart RAR extraction, passwords, recovery data, or all embedded tracks.

Online conversion requires uploading the media and may involve size limits, queue time, privacy restrictions, or recompression. Do not upload confidential, private, copyrighted, password-protected, or very large archives; 7-Zip with FFmpeg or MKVToolNix keeps the files local.

Check compatibility before finalizing

A device may support the MKV container but reject a particular video codec, audio codec, subtitle format, profile, resolution, or multiple-track layout. Inspect the result with:

ffprobe output.mkv

Check the target device or application's supported codecs and subtitle types, then stream-copy compatible streams or transcode only the incompatible ones. Extraction and remuxing preserve the encoded quality; only transcoding introduces generation loss.