SRT Validator and Cleaner: Check and Fix SRT & VTT Files

Video players forgive a lot. Editors and upload pages are stricter: one malformed line can stop a whole file from importing. The validator reads your file line by line and reports:

• Structure: timing lines that can't be read, a dot instead of a comma in timestamps, missing hours, missing blank lines between cues, wrong or repeated cue numbers, empty cues, and text before the first cue.
• Timing: captions that end before they start or never show, overlapping captions, cues out of time order, and tiny gaps that make captions blink.
• Readability: lines over 42 characters, more than 20 characters per second, and captions on screen for under 0.8 seconds.
• Encoding: garbled accents like "é" for "é" (recoverable) and characters already lost as "�" (not recoverable).

Every problem shows the line or cue number, so you can find it in your editor. Use it as a subtitle checker before you upload: the SRT validator online reads every cue in your browser.

The repair only makes changes that have one correct answer:

• Rewrites timing lines in standard SRT format (00:01:02,500 --> 00:01:04,000) without changing any time.
• Adds missing blank lines, renumbers cues 1, 2, 3, removes empty cues, and puts cues in time order.
• Restores garbled characters when the original text can be recovered exactly.
• Ends an overlapping caption when the next one starts, only if it still stays on screen for at least 0.7 seconds and keeps at least half its time.

It never rewrites dialogue and never guesses at timing. A caption that ends before it starts, or one nested inside another, stays as it is and appears under "Needs a decision", because the right answer isn't in the file. If a timing line can't be read at all, the repair waits until you fix that line, so no dialogue is dropped.

• Check the cue count first. If it's well below what the file should hold, look for a "can't be read" line near where the count stops: one malformed timing line can hide every cue after it in a strict editor.
• Errors before warnings. Errors stop imports or show the wrong caption: unreadable timing, missing blank lines, overlaps, captions that end before they start. Warnings are readability problems that won't stop a file being accepted.
• Overlaps cascade. One caption stretched too far runs into the next, which can then run into the one after. Fixing the earliest one often clears several reports, so check again after each manual edit.
• Every caption a little late? That's a sync problem, not a broken file. No validator can see it, because it needs the video. Use the delay fixer instead.