Subtitle QC Checker

Subtitle QC Checker runs four quality checks over a SubRip file in one pass and returns a numbered report of what it found. Paste your subtitles into the SRT Content box, run it, and you get either a list of issues naming the cue and the measured value for each, or a short confirmation that the file passed - saveable as a .txt file for your delivery paperwork.

Every delivery reaches a moment where someone must declare the file fit to ship, and platforms, broadcasters and accessibility auditors screen for broadly the same faults. Overlapping cues make a player stack or drop captions. Cues that flash by in under a second cannot be read. Text crammed into too little time is present but functionally invisible. Over-long lines wrap unpredictably or run off the television safe area.

The checks are concrete. Cues are walked in order and any cue starting before the previous one ended is flagged as an overlap. Any cue displayed for less than one second is reported with its duration to two decimals. Reading speed is computed per cue and anything above 21 characters per second is flagged as fast, the usual adult-audience ceiling. Each line inside a cue is measured separately and any line beyond 42 characters is reported with its exact length. The report opens with the issue count, so you know at once whether you face three fixes or three hundred.

This is a diagnostic tool: it reports and never rewrites, and it runs entirely in your browser with nothing uploaded, so pre-release material can be screened safely.

• Overlap detection: Cues are compared in sequence and any cue that begins before the previous cue has ended is named in the report, catching the timing collisions that make players drop or double-stack captions.
• Minimum display time: Any cue shorter than one second is flagged along with its measured duration to two decimals, so you can tell a borderline 0.95-second cue from a 0.20-second flash.
• Per-cue reading speed: Characters per second is calculated for each cue individually and anything over 21 cps is reported with its actual value, which finds the fast cues that a file-wide average would hide.
• Line length limit: Every line inside a cue is measured on its own and any line exceeding 42 characters is reported with its exact character count, matching the width most broadcast style guides enforce.
• Issue count up front: The report opens with the total number of issues found, which tells you at a glance whether the file needs a quick touch-up or a full retime.
• Cue numbers on every finding: Each line of the report names the cue it refers to, so you can jump straight to the offending block in your editor rather than hunting for it.
• Explicit pass result: A clean file returns a clear confirmation that no overlap, timing, reading-speed or length problems were found, which is a defensible thing to record on a delivery note.
• Report-only by design: Nothing in your file is altered, so the checker is safe to run on a locked deliverable and can be repeated after each round of fixes.

1. Select the entire contents of the subtitle file you are about to deliver and paste it into the SRT Content box.
2. Click Load sample first if you want to see the report format, since the sample deliberately includes a very short cue that trips the display-time check.
3. Click Run to perform all four checks in a single pass.
4. Read the issue count on the first line of the report to judge the scale of the work, then work down the list, which names each affected cue number and the measured value.
5. Fix the flagged cues in your subtitle editor - extend short cues, separate overlapping timings, condense text on cues above 21 cps and split lines over 42 characters.
6. Paste the corrected file back in and run the checker again, repeating until you get the clean pass message.
7. Save the passing report with the download button as a .txt file and attach it to the delivery as evidence that the file was screened.

Example 1 - a file with three distinct faults. One cue is far too brief, another collides with its predecessor, and a third carries a line beyond the standard width.

QC Report - 3 issue(s):
Cue 4: too short (0.50s).
Cue 4: 62.0 cps (fast).
Cue 7: overlaps previous.
Cue 9: 51 chars/line.

Example 2 - the cue behind a flagged line. Cue 4 below shows why two checks fire at once: 31 visible characters in half a second is unreadable, and lengthening the cue fixes both findings together.

4
00:00:18,000 --> 00:00:18,500
He never came back after that.

Corrected:
4
00:00:18,000 --> 00:00:20,200
He never came back after that.

Fixing timing usually clears the reading-speed flag as a side effect, so it is worth addressing duration problems before rewriting any text.

• One gate instead of four: Overlaps, display time, reading speed and line length are all screened in a single run, so a pre-delivery check takes a minute rather than four separate passes.
• Fewer rejected deliveries: The thresholds used here mirror what platforms and broadcasters commonly screen for, so files that pass are far less likely to bounce back from ingest QC.
• Better accessibility outcomes: Eliminating flash-frame cues and unreadably fast text is the difference between captions that technically exist and captions a deaf or hard-of-hearing viewer can genuinely follow.
• Precise, actionable findings: Because each issue names its cue number and its measured value, corrections are targeted rather than a speculative sweep through the whole file.
• Documented sign-off: A saved pass report gives you something concrete to attach to a delivery when a client or broadcaster asks how the file was checked.
• Safe to run on anything: The checker never modifies your subtitles and never uploads them, so a locked, embargoed deliverable can be screened without risk.