FormatDrop
How-To Guide

How to Convert AVI to MKV

MKV (Matroska) is the modern, feature-rich alternative to AVI. It supports any codec, multiple audio tracks, subtitles, chapters, and metadata — while AVI supports almost none of those. Converting AVI to MKV can often be done losslessly (remuxing without re-encoding), preserving every bit of the original video.

Open AVI to MKV Converter

Step-by-step instructions

  1. 1

    Lossless remux with FFmpeg (no quality loss)

    Most AVI files contain DivX, Xvid (MPEG-4 Part 2), or H.264 video with MP3 audio. Remux these into MKV without re-encoding: `ffmpeg -i input.avi -c copy output.mkv`. This is instant regardless of file size, lossless, and just changes the container. If video or audio is wrong, try full re-encoding instead.

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  2. 2

    Re-encode to H.264 MKV (better compression)

    To re-encode to modern H.264: `ffmpeg -i input.avi -c:v libx264 -crf 20 -c:a aac output.mkv`. Or H.265 for smaller files: `ffmpeg -i input.avi -c:v libx265 -crf 24 -c:a aac output.mkv`. Re-encoding takes longer but produces much smaller files with modern codecs.

  3. 3

    Use MKVToolNix for lossless remuxing (GUI)

    Download MKVToolNix (mkvtoolnix.download — free, all platforms). Open MKVMerge GUI. Drag in your AVI file. MKVToolNix shows all tracks (video, audio, subtitles). Deselect any unwanted tracks. Click Start Multiplexing. MKVToolNix remuxes the AVI into MKV — lossless, fast, and reliable.

  4. 4

    Add subtitles during conversion

    One major advantage of MKV: you can embed SRT subtitles. With FFmpeg: `ffmpeg -i input.avi -i subtitles.srt -c copy -c:s srt output.mkv`. With MKVToolNix: drag the SRT file into the source panel alongside the AVI — both are muxed into the MKV together. The subtitles become part of the file without affecting video or audio quality.

Why convert AVI to MKV?

MKV solves AVI's biggest limitations: multiple audio tracks, embedded subtitles, chapter markers, and any codec. Converting your AVI library to MKV future-proofs it while potentially reducing file size significantly if you re-encode to H.264 or H.265.

Your files never leave your device

FormatDrop runs the conversion engine entirely inside your browser using WebAssembly. No file upload. No server. Nothing stored. You can verify this by opening DevTools → Network tab and watching: zero upload requests.

Frequently asked questions

Should I remux or re-encode AVI to MKV?
Remux (copy) if you want lossless conversion and don't care about file size or codec compatibility. Re-encode if you want to upgrade the codec (DivX or Xvid to H.264), reduce file size, or the AVI has codec issues. For archiving old AVI files, remux first — you can always re-encode later.
What codec do old AVI files usually have?
AVI files from 2000–2010 typically use DivX or Xvid (MPEG-4 Part 2) video with MP3 audio — common in downloaded movies from that era. Later AVI files may contain H.264 video. Check with FFprobe: `ffprobe input.avi`. DivX and Xvid are still supported but not hardware-decoded on most modern devices; re-encoding to H.264 improves compatibility.
Does MKV play on smart TVs and media players?
MKV support varies. Most modern smart TVs (Samsung, LG, Sony), streaming sticks (Roku, Fire TV), and media players (Kodi, Plex, VLC) support MKV. Some older smart TVs only support MP4 natively. If your target device is a smart TV, check its specifications — if MKV isn't listed, convert to MP4 instead.
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