Subtitle tools

What these tools do

Convert SRT to VTT, and VTT to SRT

SRT is the interchange format most deliveries start from; WebVTT is what browsers and most players ingest. The converter parses either and writes the other, preserving timing to the millisecond. Both store real clock time, so no frame rate is involved. Note that WebVTT cue settings (position, alignment, regions) have no SRT equivalent and are dropped when you convert in that direction, which the tool tells you at the time.

Fix subtitles that are out of sync

Two different defects hide behind "out of sync." A constant offset needs a shift. A drift that grows across the runtime is a frame-rate mismatch: a file timed for 25 fps playing against a 23.976 fps master, or 23.976 confused with 24. The retime tool applies the exact ratio, and this guide explains how to tell which defect you have from the shape of the error.

Check a file against broadcast limits

The validator runs the mechanical rules a platform QC bounces files on: line length, line count, reading speed, minimum and maximum duration, the two-frame gap, and overlaps.

It grades what it finds rather than calling everything an error, because in professional work most of these limits have legitimate exceptions. Blocking means the spec is broken with no defensible reading: a line over 42 characters, three lines, an overlap, a cue that ends before it starts. Those bounce. Review means a limit is exceeded for a reason a person has to weigh. A cue carrying two speakers splits its text between two short lines that each read comfortably; an on-screen card stacked over dialogue is two reading units by design; and dialogue that is fast in the original is often faithfully fast in translation, where condensing would cost meaning rather than add clarity. For those the tool reports the combined figure and the longest single line, so you can tell in one glance which it is. Repairable means the writer fixes it mechanically, like a gap under two frames.

It is calibrated the way a delivery is actually judged: cues of twelve characters or fewer are exempt from reading speed, and bilingual stacked files are measured per language. It does not judge the translation: a file can pass every check here and still read badly, which is a different class of problem entirely.