Convert AVI to MKV — Free & Private

Will my video be re-encoded or just remuxed when converting AVI to MKV?

This is the one AVI conversion where a remux is actually likely. Matroska (MKV) is a flexible container that accepts almost any video codec, including the DivX and Xvid streams found in most old AVI files. If your AVI's codec is one MKV supports — which covers DivX, Xvid, and H.264 — Convertlo can repackage it into MKV without re-encoding, preserving the original quality exactly. Re-encoding to H.264 is only needed if you specifically want a smaller file.

• DivX/Xvid AVI → MKV: usually a fast, lossless remux — no quality change
• H.264-in-AVI → MKV: also remuxed directly
• Choose re-encode instead of remux only if a smaller H.264 file matters more than speed

Will the output MKV play on media players like VLC and Plex?

Yes — MKV is the native format of choice for media-server software. VLC, Plex, Jellyfin, and Kodi all handle MKV, including DivX/Xvid streams carried over from the original AVI, without complaint. The trade-off is that MKV has weak support on phones and in web browsers, so it suits a media library better than general sharing.

• VLC, Plex, Jellyfin, Kodi: full native MKV support, including legacy codecs inside it
• Phones and browsers: MKV playback is patchy — MP4 is the safer choice for sharing
• MKV can hold multiple audio tracks and subtitle streams that AVI never supported

How much will the file size change going from AVI to MKV?

If Convertlo remuxes your AVI into MKV — the typical outcome for DivX/Xvid sources — the file size stays essentially the same, since only the wrapper changes, not the video data. Choosing to re-encode to H.264 instead will shrink the file, typically by 3–10x, but takes longer to process.

• Remux (default for compatible codecs): file size unchanged
• Re-encode to H.264: roughly 3–10x smaller, at the cost of processing time
• MKV's own container overhead is negligible either way

Will a MKV re-encode fix DivX/Xvid playback, or do I still need H.264?

Only the re-encode option fixes it. A remux keeps the original DivX/Xvid stream inside the MKV wrapper, which still won't play on iPhones, smart TVs, or Android. Re-encoding to H.264 inside MKV is what actually solves the problem.

• Remux (keep codec): DivX/Xvid goes into MKV unchanged — iPhone and smart TVs still can't play it
• Re-encode (H.264): converts the codec — the MKV plays in VLC, Plex, Kodi, and on most media servers
• For phones and smart TVs, use MP4 (H.264) as the output instead — it has broader device support than MKV