webUtils.uk

VTT Time Shifter: Sync WebVTT Files Online

Shift the timing of a WebVTT caption file for the web, a video player or an online course. Cue settings like position and alignment, NOTE and STYLE blocks and karaoke timestamps are all kept.

How to shift subtitle timing in 3 steps

  1. 1

    Open your .vtt file

    Drop it anywhere on the page or choose it with the button. The file stays on your device.

  2. 2

    Enter the offset

    Type a number of seconds, for example +1.5 to delay the subtitles or −0.8 to make them appear sooner. Check the “Now” column to see the new times.

  3. 3

    Download the synced file

    Click Download. The new file keeps your file name with the offset added, so you can tell it apart from the original.

What is kept in your VTT file

Only the cue timings change. Everything that makes your captions look right stays as it was:

  • The WEBVTT header and any metadata lines under it
  • Cue settings such as align:start line:90%
  • NOTE, STYLE and REGION blocks
  • Cue identifiers, and inline karaoke timestamps like <00:01:05.500>, which are shifted along with the cue

Subtitles too early, too late, or drifting?

Subtitles appear before the speech

The subtitles are ahead of the audio. Delay them with a positive offset: +2 moves every line 2 seconds later.

Subtitles appear after the speech

The subtitles are behind the audio. Speed them up to match with a negative offset: −1.5 brings every line 1.5 seconds earlier.

In sync at the start, wrong by the end

The gap grows because the subtitles were timed for a different frame rate. Set “Subtitles timed for” and “Your video plays at”, then fine-tune with an offset.

Frequently asked questions

Subtitles appear too early. Do I add or subtract time?

Add time. A positive offset such as +2 makes every subtitle appear 2 seconds later. If the subtitles appear too late, subtract time with a negative offset such as −2.

How do I calculate the time offset?

Play the video and pause on a line of dialogue. Note the time the person starts speaking and the time the subtitle appears. The difference is your offset. If the subtitle appears 1.5 seconds before the voice, enter +1.5. If it appears 0.8 seconds after, enter −0.8.

Easier still: open “Match a line, frame rate and format”, type the cue number and when that line is actually spoken, and the offset is worked out for you.

Which subtitle formats does it support?

SRT (SubRip), WebVTT (.vtt), ASS and SSA (Advanced SubStation Alpha) and SBV (YouTube captions). It can also convert any of them to SRT or WebVTT while it shifts them.

Are my files uploaded to your server?

No. Your subtitle file is read and rewritten by your own browser. Nothing is uploaded, nothing is stored, and the tool keeps working if you go offline after the page has loaded.

Only part of my file is out of sync. Can I fix just that part?

Yes. Under “Match a line, frame rate and format”, set Start shifting at cue to the first line that is wrong. Lines before it keep their original times. This is the usual fix after an ad break or a scene that was cut from your copy.