Subtitle timing inspector

How to use this application

Use the subtitle timing inspector before delivering a caption file or moving subtitles between editing tools. Paste the text of a SubRip SRT file or a basic WebVTT file, then choose Inspect subtitles. The report shows cue count, latest cue end, timing overlaps and the highest character pace. A cue table keeps each caption beside its start, end, duration and character count, so you can compare the timing with your editing timeline. The app does not upload a video or contact a subtitle service.

For SRT, use timestamps such as 00:00:01,500 --> 00:00:03,000, with a caption underneath and a blank line between cues. Numeric identifiers are accepted, and a timing line can also begin a block without an identifier. For WebVTT, begin with WEBVTT followed by a blank line. Use decimal-point timestamps such as 00:01.500 or 00:00:01.500. Optional cue identifiers are accepted. NOTE blocks are skipped. Timing-line settings are ignored and counted in the report; their layout meaning is not checked. STYLE and REGION blocks, header metadata, and inline timing tags are outside the supported basic subset.

Load the example to inspect three captions. The second starts at 1.800 seconds while the first ends at 2.000 seconds, so the report identifies one overlapping cue. The final cue ends at 5.000 seconds. An overlap can be intentional when two speakers talk together; review the flag against your media rather than removing every overlap automatically. Out-of-order start times are flagged separately, and are compared in the supplied file order. An end time equal to or earlier than its start is rejected because it cannot provide a positive display duration.

Character pace divides a caption’s character count by its duration in seconds. Counting uses Unicode code points, includes spaces and punctuation, and turns each line break into a space. Angle-bracket markup is excluded from this count, and the common amp, lt, gt, nbsp, lrm and rlm entities receive basic handling. Other entities remain as written. Combining marks and emoji sequences can contain multiple code points, so this is not a count of visual glyphs or screen width. Raw caption text is displayed as text, never interpreted as HTML. No universal reading-speed threshold is applied. A high pace value is a prompt for human review, not a certification that captions are accessible or inaccessible.

After a successful inspection, choose Save complete timing report to download a standalone HTML handoff containing every accepted cue and every timing flag, including entries omitted from the on-screen preview. The report keeps cue order, supplied identifiers, caption text, start/end times, duration and character pace. It opens without JavaScript or a network connection. It contains all supplied caption text: share it only with intended recipients. This is a review report, not a repaired subtitle file; review any observations against the media in your editing tool.

Editing the source clears the previous report immediately. Inspect again after making a change, or choose Clear to remove both the input and report. Reloading or closing the page also clears the working state. Inputs stay in temporary page memory: there is no account, saved subtitle history, persistent browser storage, remote processing or background transmission.

The interface accepts up to 250,000 characters and 1,000 cues. The table displays the first 200 cues and the notice list displays the first 50 timing flags; the summary still includes every accepted cue. Hours are limited to two or three digits, with two-digit minutes and seconds and exactly three millisecond digits. Missing cue separators, empty captions and malformed timing lines need correction before a report can be produced. This tool does not rewrite your file, validate a complete WebVTT specification, play media, judge audio synchronization, measure text contrast or check a delivery platform’s rules. Use your editor and the receiving platform’s requirements for that final review.

Technical reference: W3C WebVTT specification (Candidate Recommendation Draft).