How to Remove Duplicate Lines from YouTube Captions
Distinguish exact duplicate cues from rolling auto-caption fragments and remove repetition without deleting intentional speech.
Duplicate captions come in at least three forms: identical cue text repeated at different times, consecutive lines duplicated inside one cue, and rolling auto-caption fragments that overlap only partly. Exact-line removal solves the second case, but using it on a whole subtitle file can delete legitimate repeated speech such as “No, no, no.”
Classify before deleting
Exact adjacent duplicate:
12
00:00:30,000 --> 00:00:32,000
Open the caption settings.
13
00:00:32,050 --> 00:00:34,000
Open the caption settings.
Listen to the audio. If the speaker says it once, merge the useful time range. If the speaker repeats it, both cues are valid.
Duplicate lines inside a cue:
Save the source file.
Save the source file.
Then create a working copy.
This can usually become two lines. A general duplicate line remover helps with plain text, but timestamps and cue boundaries require subtitle-aware review.
Rolling overlap:
we will export
we will export the captions
export the captions as srt
Exact comparison finds no duplicates. The intended sentence is “We will export the captions as SRT.” Compare suffixes and prefixes of neighboring cues, then rebuild the sentence against audio.
A cautious cleanup algorithm
Normalize whitespace for comparison but keep original text for output. Compare adjacent cues first, not every cue in the file. Mark exact matches, containment (A is entirely inside B), and suffix-prefix overlap. Require close timestamps before suggesting a merge. Present suggestions for review instead of deleting automatically.
Case-insensitive matching can help, but punctuation differences may be meaningful. Let's eat, Grandma and Let's eat Grandma should not be treated as safely identical.
Preserve timing when merging
If two cues are artifacts of one utterance, use the earliest valid start and the end that matches the end of speech. Then check reading time:
12
00:00:30,000 --> 00:00:34,000
Open the caption settings.
Do not automatically take the latest end if it covers the next speaker or a scene change. If merged text becomes long, split at a natural phrase and retime.
Audit the result
Compare cue count before and after, review every removed cue, and search for empty blocks. Play all merge points. Keep a log such as merged 12+13: rolling duplicate so another reviewer can undo questionable edits.
Duplicate cleanup is one part of cleaning auto-generated captions. If merged time ranges collide with following cues, use the overlap repair guide. The complete YouTube subtitle workflow keeps cleanup separate from conversion and translation.