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Subtitle file timing and readability check

PL by Prompier Library ☆☆☆☆☆ New Version 1 · updated Nov 10, 2026
Reviewed by moderator Prompier Library on Nov 10, 2026. Checked for personal data, secrets, risky instructions and a clear license.

About this prompt

Audits subtitle or caption text for timing errors, reading speed and line-length problems, then returns a fixed version of the problem cues. Use before publishing a video with captions.

Prompt text

You are a careful caption editor. Check the subtitle file below against the limits I give you, then fix only the cues that break them. Inputs: - Subtitle file text (SRT or WebVTT): {{subtitle_text}} - Maximum characters per second: {{max_cps}} - Maximum characters per line and lines per cue: {{line_limits}} - Shortest and longest cue duration: {{duration_limits}} Steps: 1. Read the whole file before judging. Note the format and the numbering style used. 2. Check every cue for: start time after end time, overlap with the next cue, gaps in numbering, empty text, reading speed above the limit, lines or line counts above the limit, cues shorter or longer than allowed, and unbalanced formatting tags. 3. For each problem cue, propose the smallest fix: split a long cue, merge a flash cue, rebalance line breaks, or nudge timing. Never change the meaning or spelling of the spoken words. If a fix would need audio you cannot hear, say so instead of guessing. 4. If a required limit is missing, assume common defaults (about 17 characters per second, 42 characters per line, 2 lines) and state that you did so. Ask at most 3 questions only if the file itself is unreadable. Output format: - Summary: total cues, number with problems, the 3 most common issues. - Problem table: cue number | issue | original timing | fixed timing. - Corrected file: only the changed cues, in the original format, followed by the sentence "All other cues unchanged." - Open questions: anything that needs a human check against the video. Quality bar: do not invent dialogue, do not retime cues without saying why, keep numbering continuous after splits or merges, and keep sound labels in the style already used.

Variables

4 variables
VariableWhat to enterExampleDefault
{{subtitle_text}}Paste the subtitle file text1 00:00:01,000 --> 00:00:03,500 Welcome back to the kitchen. 2 00:00:03,600 --> ...—
{{max_cps}}The most characters per second viewers should read17 characters per second—
{{line_limits}}Maximum characters per line and lines per subtitle42 characters per line, 2 lines—
{{duration_limits}}The shortest and longest time a subtitle should stay on screenShortest 1 second, longest 7 seconds—

Try it

Live preview
Paste the subtitle file text
The most characters per second viewers should read
Maximum characters per line and lines per subtitle
The shortest and longest time a subtitle should stay on screen
Your finished prompt
You are a careful caption editor. Check the subtitle file below against the limits I give you, then fix only the cues that break them. Inputs: - Subtitle file text (SRT or WebVTT): {{subtitle_text}} - Maximum characters per second: {{max_cps}} - Maximum characters per line and lines per cue: {{line_limits}} - Shortest and longest cue duration: {{duration_limits}} Steps: 1. Read the whole file before judging. Note the format and the numbering style used. 2. Check every cue for: start time after end time, overlap with the next cue, gaps in numbering, empty text, reading speed above the limit, lines or line counts above the limit, cues shorter or longer than allowed, and unbalanced formatting tags. 3. For each problem cue, propose the smallest fix: split a long cue, merge a flash cue, rebalance line breaks, or nudge timing. Never change the meaning or spelling of the spoken words. If a fix would need audio you cannot hear, say so instead of guessing. 4. If a required limit is missing, assume common defaults (about 17 characters per second, 42 characters per line, 2 lines) and state that you did so. Ask at most 3 questions only if the file itself is unreadable. Output format: - Summary: total cues, number with problems, the 3 most common issues. - Problem table: cue number | issue | original timing | fixed timing. - Corrected file: only the changed cues, in the original format, followed by the sentence "All other cues unchanged." - Open questions: anything that needs a human check against the video. Quality bar: do not invent dialogue, do not retime cues without saying why, keep numbering continuous after splits or merges, and keep sound labels in the style already used.

Sample output

Summary: 84 cues checked, 11 with problems. Most common: reading speed too high (6), line too long (3), overlap (2). Cue | Issue | Original | Fixed 12 | 24 chars/sec, limit 17 | 00:01:02,100 --> 00:01:03,300 | 00:01:02,100 --> 00:01:04,000 31 | Overlaps cue 32 by 0.4 s | 00:02:10,000 --> 00:02:13,400 | 00:02:10,000 --> 00:02:13,000 47 | Line of 58 chars | one line | split into two balanced lines Corrected cues: 12 00:01:02,100 --> 00:01:04,000 We will cover pricing first. ... All other cues unchanged. Open question: cue 59 shows only a music label for 9 seconds; check whether dialogue was missed.

An example the author shared. Your result will differ.

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