Subtitle quality control
Subtitle QC Checklist
Run every subtitle delivery through this checklist before you export. It covers the checks that reject files at the platform level — reading speed, line discipline, timing and sync — in the order they are quickest to catch.
Confirm format and encoding
Verify the file is the format the platform expects (SRT or WebVTT) and saved as UTF-8 with no stray BOM or control characters.
Check reading speed per cue
Divide each cue's visible characters by its duration. English adult content should stay at or under 20 CPS; children's content under 17 CPS.
Check line length and line count
Keep each line at 42 characters or fewer and each cue at two lines or fewer. Prefer a single line; only break to a second line when the text exceeds the limit.
Check minimum and maximum duration
Each cue should stay on screen at least 5/6 of a second (20 frames at 24 fps) and no longer than 7 seconds. Split any cue over 7 seconds.
Check the gap between cues
Leave at least a 2-frame gap between consecutive cues. At 24 fps, close any 3–11 frame gaps to 2 frames so gaps are either 2 frames or half a second plus.
Check timing and sync
Confirm in-times land on the first frame of audio and out-times match the speech. Flag overlapping cues and any cue that ends before it starts.
Check line breaks
Break after punctuation and before conjunctions or prepositions. Never split an article from its noun, an adjective from its noun, or a first name from a last name.
Proofread text and punctuation
Review spelling, grammar, capitalization and punctuation. Keep numbers, currency and brand names as they appear on screen unless the style guide says otherwise.
Check forced narratives and SDH labels
Keep on-screen text (forced narratives) separate from dialogue, and confirm SDH sound labels and speaker changes are present and correctly formatted where required.
Watch the file back
Play the full file against the video to catch anything a spreadsheet check misses: flicker, lingering captions, or subtitles covering on-screen text.
Automate the first pass
The subtitle reading speed checker reports CPS, line length and timing for every cue at once, and the QC report generator turns that into a deliverable CSV. Use them to catch mechanical issues, then spend your watch-back on the judgment calls.