AiLounge Tools

Subtitle Format & Timing Toolkit

Convert SRT/VTT, shift whole timelines, and merge bilingual subtitles by time-overlap ratio — entirely in your browser, with no upload.Processed locally · no upload

From SRT to bilingual subtitles: a three-step timeline cleanup

This tutorial uses all three real operations, entirely locally. Start with a UTF-8 SRT containing two cues, one crossing 00:00:59,999.

  1. Convert SRT/VTT: open srt-vtt, paste the subtitle into "Subtitle text" or pick a .srt file, keep source encoding "Auto (UTF-8)", input format "Auto-detect" and output "Auto convert". The result starts with WEBVTT, uses a dot for milliseconds, drops cue numbers and keeps correct blank lines. Paste it back and choose SRT to convert the other way.
  2. Shift the timeline: open offset, use the same subtitle and enter 1500 ms. 00:00:59,999 becomes exactly 00:01:01,499. A negative offset that would create negative starts is rejected by default with guidance; switch the negative-start policy to "Clamp to 0" to get output plus an impact count. end is never smaller than start.
  3. Merge bilingually: open bilingual and provide the primary and secondary subtitles separately. Counts may differ and timelines may be slightly shifted; minimum overlap defaults to 0.5. Pairs are chosen by temporal overlap, e.g. primary 00:00:01,000-->00:00:03,000 matches secondary 00:00:01,100-->00:00:03,100; unmatched cues are listed separately. The preview is plain text; copy or download SRT/VTT, and download the original file too.

For legacy GBK files choose GBK in "Source encoding" first; otherwise the tool asks you to choose an encoding instead of producing mojibake. VTT NOTE / STYLE / REGION blocks and inline positioning are not preserved — download the original before converting.

Open the tool