SRT Subtitle File Validator — Timing & Format Checks

What does an SRT validator check?

An SRT validator checks cue numbering, comma-millisecond timestamps, timing order, overlaps, gaps, duration, reading speed, and line limits. Subtitle Preflight runs these checks in the browser and reports issues without editing or uploading the file.

Choose an .srt file or paste supported SRT text to begin.

Check a supplied subtitle file

Supported: .srt, .vtt, and .webvtt text files. Current browser-local limits: 5 MiB and 10,000 cues.

Or drag and drop one supported subtitle file here.

Privacy: Analyzed in this browser; subtitle contents are not sent to our application server in the default workflow.

Synthetic example created for Subtitle Preflight; CC0

Findings

No subtitle loaded

No subtitle loaded

Choose a file, paste subtitle text, or load a synthetic sample to see cue-level findings here. Export becomes available after analysis succeeds.

Ready for a subtitle fileChoose an SRT or WebVTT file, paste subtitle text, or load a synthetic sample.

Technical/readability preflight only — not certification or a substitute for media review.

The checker does not compare subtitles with audio or video and cannot verify accuracy, completeness, speaker identification, meaningful sounds, visual placement, accessibility or legal conformance, or client/platform acceptance.

SRT structure at a glance

An SRT cue normally contains a numeric sequence value, one timing line, one or more text lines, and a blank line before the next cue. This parser expects comma-millisecond timestamps in the form HH:MM:SS,mmm --> HH:MM:SS,mmm.

Minimal valid SRT example

1
00:00:01,000 --> 00:00:03,000
Synthetic subtitle example.

2
00:00:03,120 --> 00:00:05,000
Second synthetic cue.

Synthetic example. The second cue starts after the first cue ends and uses a blank line between blocks.

Invalid SRT example

1
00:00:01.000 --> 00:00:03.000
Dot milliseconds are not accepted by this SRT parser.

3
00:00:04,000 --> 00:00:03,500
The sequence skips 2 and the end is not after the start.

Synthetic example. The parser reports dot-millisecond syntax, the sequence gap, and the invalid timing order. It does not repair the file.

Common SRT errors this validator reports

Issue	Expected syntax or condition	Finding or diagnostic ID	What to review
Missing or out-of-sequence cue number	Numeric cue values follow the expected sequence	`SRT_INDEX_MISSING_OR_OUT_OF_SEQUENCE`	Check the cue number and nearby block boundaries.
Invalid SRT timestamp	`HH:MM:SS,mmm --> HH:MM:SS,mmm`	`TIMESTAMP_SYNTAX_INVALID`	Replace dot milliseconds or malformed timing punctuation in the source file.
End time is not after start time	Cue end must be later than cue start	`TIMESTAMP_END_NOT_AFTER_START`	Review the cue start and end values.
Overlapping adjacent cues	A cue should not start before the previous cue ends	`CUE_OVERLAP`	Confirm whether the overlap is intentional for the delivery workflow.
Gap below selected minimum	Gap is at least the selected profile value	`GAP_BELOW_PROFILE_MIN`	Compare the adjacent cue boundary with the selected profile.
Duration outside selected range	Cue duration stays within the selected profile range	`DURATION_BELOW_PROFILE_MIN` or `DURATION_ABOVE_PROFILE_MAX`	Review timing and the selected profile; do not treat the default as universal.
Reading speed above selected maximum	CPS and WPM do not exceed selected profile values	`CPS_ABOVE_PROFILE_MAX` or `WPM_ABOVE_PROFILE_MAX`	Review cue text, duration, language, and the actual delivery requirement.
Too many lines or characters per line	Line values stay within selected profile limits	`LINE_COUNT_ABOVE_PROFILE_MAX` or `CHARS_PER_LINE_ABOVE_PROFILE_MAX`	Review line breaks and the applicable client or platform rule.
Empty cue text	A parsed cue contains visible text	`CUE_TEXT_EMPTY`	Check whether text is missing or the block is malformed.
Adjacent duplicate text	Adjacent cues do not contain the same normalized text	`ADJACENT_TEXT_DUPLICATE`	Confirm whether the repetition is intentional.
Malformed SRT block	Block contains supported sequence, timing, and text structure	`SRT_BLOCK_MALFORMED`	Review the reported source line and surrounding blank lines.

What this SRT validator supports

.srt file selection and pasted SRT text;
numeric cue sequence checks;
comma-millisecond timestamp parsing;
recoverable parser diagnostics with source-line context;
deterministic timing, duration, CPS, WPM, line, empty-text, and adjacent-duplicate findings;
editable named rule profile;
local CSV and self-contained HTML export after a fresh check.

What it does not verify

The checker does not edit or repair the supplied SRT file. It does not compare subtitles with audio or video, and it cannot verify transcription accuracy, completeness, speaker identification, meaningful sounds, visual placement, accessibility or legal conformance, or acceptance by a client or platform.

Technical/readability preflight only — not certification or a substitute for media review.

Review an SRT file before delivery

Run the browser-local check, inspect each cue-level finding, and download a local report when the result is fresh.

Check an SRT file locally Compare SRT and WebVTT

Frequently asked questions

Does the SRT validator upload my subtitle file?

In the implemented default workflow, parsing, checks, and report generation run in your browser. Subtitle content is not intentionally sent to an application server.

Does it repair invalid SRT files?

No. The checker reports supported parser and rule findings without changing the supplied file.

Should SRT timestamps use commas or dots?

This declared SRT parser expects commas for milliseconds, as in 00:00:01,000. Dot-millisecond syntax is reported as invalid SRT timing.

Does a clean SRT report prove accessibility compliance?

No. A file-only technical and readability preflight cannot verify source media, legal conformance, or client and platform acceptance.

Can I change the reading-speed and line limits?

Yes. Edit the visible profile for the applicable workflow, then rerun the check so the findings and export use the current values.