Fix and Validate Subtitle Files
Players choke on subtitle files with overlapping cues, cues that end before they start, empty blocks or broken numbering. This tool validates your file, lists every problem with its cue number, and downloads a repaired version. It also flags lines that read faster than 21 characters per second so you can shorten them.
Accepted: .srt, .vtt, .sbv
Your files never leave your device.
How to use this tool
- Drop your subtitle file on the box above.
- Read the validation report — each issue shows the cue number and what is wrong.
- Download the fixed file. Reading-speed warnings are for you to edit manually.
What gets checked
The validator looks for overlapping cues (a cue starts before the previous one ends), zero or negative durations, empty cues, cues that are out of chronological order and cues whose reading speed exceeds 21 characters per second — the ceiling used by Netflix and most broadcasters for comfortable reading. Each finding is listed with its cue number, severity and a one-line explanation so you can locate it in your editor.
What gets fixed automatically
Auto-fix sorts cues by start time, removes cues with no text, gives zero- or negative-length cues a one-second duration, resolves overlaps by trimming the earlier cue (or nudging the later one when trimming would leave it too short), tidies stray whitespace and renumbers everything from 1. Timing of healthy cues is never touched.
Reading-speed problems are deliberately left alone. Fixing them requires either rewriting the text or extending the display time into the next cue, both of which need human judgement. The report tells you exactly which cues to look at.
Tolerant parsing comes first
Before validation even starts, the parser copes with missing cue numbers, dots used as millisecond separators, hour-less timestamps, mixed line endings, byte-order marks and Windows-1252 encoded text. Those structural problems are repaired silently and reported as warnings on the file card, so even a badly mangled file produces a clean, standards-compliant result in the same format you uploaded.
Frequently asked questions
- Why is 21 characters per second the limit?
- It is the reading speed most style guides, including Netflix’s, consider the maximum for adult viewers. Lines above it are hard to finish before they disappear. Children’s content usually uses lower limits.
- Will the fix change my text?
- Only whitespace is trimmed and completely empty cues are removed. Wording, formatting tags and line breaks inside cues stay exactly as they were.
- My file had no issues — why download anyway?
- The downloaded copy is normalised: sequential numbering, consistent line endings, UTF-8 encoding and standard timestamps. That alone solves many player compatibility problems.
- Is my file sent to a server for analysis?
- No. Validation and repair run in your browser. The site has no backend, so there is nowhere to send the file.