# Subtitle converter: SRT, WebVTT, ASS and SBV, with time shift, frame-rate change and a validation report > Convert subtitles between SRT, WebVTT, ASS/SSA and YouTube SBV in your browser. Shift every cue earlier or later, re-time subtitles for a different frame rate (23.976 to 25 and back), re-wrap long lines, split cues that run too long, and get a report of overlaps, negative durations and bad timestamps. Files are never uploaded. By TranscribeBench. Updated 7 October 2026. Canonical URL: https://transcribebench.com/subtitle-converter/ > **Interactive converter.** Open the HTML version of this page (https://transcribebench.com/subtitle-converter/) to convert SRT, WebVTT, ASS/SSA and SBV subtitles, shift timings, change the frame rate, re-wrap long lines and get a validation report. It runs in your browser; the file is never uploaded. ## What each format can hold The converter reads every format into the same list of cues (start, end, text) and writes that list out again. Anything a format cannot hold is dropped on the way, and the report says so.
| | SubRip (.srt) | WebVTT (.vtt) | ASS / SSA (.ass, .ssa) | YouTube SBV (.sbv) | |---|---|---|---|---| | Timestamp | `00:01:02,500` | `00:01:02.500` (hours optional) | `0:01:02.50` (hundredths) | `0:01:02.500` | | Precision | 1 ms | 1 ms | 10 ms | 1 ms | | Cue numbers | Required, ignored on reading | Optional identifiers, kept | None | None | | Italic, bold, underline | `` `` `` | `` `` `` | `{\i1}` `{\b1}` `{\u1}` | No formatting | | Position, colour, fonts | `` only (not standard) | Cue settings, `STYLE` blocks | Full styling and positioning | None | | Speaker names | No | `` voice tags | `Name` field | No | | Used by | Most players and editors | HTML5 video, YouTube, Vimeo | Anime fansubs, Aegisub | YouTube Studio |
Conversions keep italic, bold and underline between SRT, WebVTT and ASS. WebVTT voice tags become "Name: " at the start of the line, because SRT and SBV have no speaker field. WebVTT cue settings (position, alignment) are kept when the output is WebVTT and dropped otherwise. ASS styling beyond italic, bold and underline is dropped when converting to another format; converting ASS to ASS (to shift times, for example) keeps the original script info, styles, fields and override tags of every cue whose text you did not change. ASS stores hundredths of a second, so converting to ASS rounds times to the nearest 10 ms. ## Fixing subtitles that drift: frame rates If subtitles start in sync and slowly drift further off, they were timed for a video at a different frame rate. The usual case is a film at 23.976 frames per second released in a 25 fps (PAL) country: the video plays about 4% faster, and an hour of film lasts 57.5 minutes. The fix multiplies every time by the ratio of the two rates: ``` new time = old time x (frame rate the subtitles were made for / frame rate of your video) ``` From 23.976 to 25 fps, the factor is (24000/1001) / 25 = 0.959041, so a cue at 1:00:00.000 moves to 57:32.547. The converter uses the exact NTSC rates (23.976 is really 24000/1001 and 29.97 is 30000/1001). The rounded figures would be off by about 4 ms per hour: small, but there is no reason to add it. If subtitles are off by the same amount all the way through, it is not a frame-rate problem. Use the shift instead: a positive number of milliseconds shows every cue later, a negative one earlier. Cues pushed before 0:00 are trimmed to start at 0:00, or dropped if they would end before it. When both are set, the frame-rate change is applied first and the shift second, so the shift is measured on your video's timeline. **Two-point sync** fixes both at once. Play the video, note when the first and last lines are actually spoken, and enter those two times. The converter moves the first cue to the first time and the last cue to the last, and stretches everything between in proportion (new time = old time x rate + offset, solved from the two points). It reads the *start* of the first and last cue, so pick lines that start on a spoken word. It runs after the frame-rate change and the shift; leave those at zero when you use it. ## Line length and cue splitting Subtitle style guides set a limit on characters per line so a line can be read at a glance. Netflix's English guide allows 42 characters per line and two lines per cue, and many broadcasters use 37 to 42. The converter's default is 42 and two lines; change both to match your platform. With **Re-wrap long lines** on, a cue that breaks the limits is wrapped again at word boundaries into lines of similar length (when two lines are needed, the split that makes the longer line shortest wins). A cue whose text cannot fit in the allowed lines is split into several cues. Its time is shared in proportion to the characters in each part, and italic or bold that runs across the split is closed and reopened, so every cue stays valid. Cues that already fit are left exactly as they were. A single word longer than the limit gets a line of its own. **Merge flash cues** joins a cue shorter than 1.2 seconds to its neighbour when the gap between them is at most half a second, the result lasts no more than 7 seconds, and the joined text still fits the line limits. ## What the validation report checks | Check | Level | Why it matters | |---|---|---| | Bad timestamp (unparseable, minutes or seconds of 60 or more) | Error, cue skipped | Players reject the file or skip the cue. | | Cue ends before it starts | Error | The cue never shows; some players reject the whole file. | | Starts and ends at the same time | Warning | The cue never shows. | | Overlaps the previous cue | Warning | Two cues on screen at once, or one hidden, depending on the player. **Fix overlaps** sorts the cues and trims each one to end where the next begins. | | Starts before the cue above it | Warning | Some players and YouTube skip cues that are out of order. | | Empty text | Warning | A blank flash on screen. | | Missing blank line, junk between cues, cue number that is not a number, missing `WEBVTT` header | Warning | The file is malformed; the converter reads it anyway and writes a clean one. | | Line longer than the limit, more lines than the limit | Note | Hard to read, especially on phones. | | More than 20 characters per second | Note | Viewers cannot finish reading. Netflix's adult English limit is 20. | | Shown for less than 0.7 seconds | Note | Too short to read. | Every issue names the cue number and the line in your file, so you can find it in an editor. ## Encodings Files are read as UTF-8 (with or without a byte-order mark) or UTF-16 with a byte-order mark. A file that is not valid UTF-8, typical of older .srt files from Windows, is read as Windows-1252, and the result names the encoding it used. Output is always UTF-8. Choose Windows line endings if an old player needs them. ## Privacy The file is read by your browser and converted in the same tab. It is never uploaded, and the page keeps working with the network switched off. See the [privacy page](/privacy/). If your subtitles came from a speech-to-text tool, the [WER calculator](/wer-calculator/) shows how many words it got wrong, and the [benchmark](/whisper-baseline-benchmark/) shows how open-source Whisper models do on recordings like yours.