Mkv: Index

Download MediaInfo (GUI or CLI). Open your MKV and look under the "Menu" section. If you see "Seek head" list and "Cues" with a count >0, you have an index. If the "Menu" section is completely absent, you have no index.

This is the primary function. A healthy index allows instantaneous and precise jumping to any point in the video. A missing or corrupted index forces the player to read the file sequentially from the beginning until it reaches the desired time—a process that can take seconds or even minutes. mkv index

# Strip cues (not recommended for playback)
mkvpropedit input.mkv --delete cues

If an MKV has no index or a corrupted index: Download MediaInfo (GUI or CLI)

# Using MKVToolNix (preserves all tracks)
mkvmerge -o output.mkv --cues 0:all input.mkv
| Symptom | Likely cause | Recovery |
|---------|--------------|----------|
| Seeking freezes or jumps to wrong time | Corrupt CueClusterPosition values | Re-mux with mkvmerge |
| Player says "Index not found" | Missing Cues element | Re-mux with cues enabled |
| Video seeks correctly but audio lags | Mismatched track numbers in cues | Re-mux with ffmpeg -c copy |
| File plays but seeking is very slow | Sparse or no index | Add full index via re-mux | If an MKV has no index or a
Note: Many hardware players (smart TVs, Blu-ray players) require a valid index; otherwise, they will not play the file at all.