Whole-timeline offset

Add an exact integer-millisecond offset to every cue (positive or negative). +1500 ms is exact, end is never smaller than start; negative starts are rejected by default with guidance, or clipped to 0 with an impact count.

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Inputs and parameters

input — Subtitle text
inputFile — Or choose a subtitle file (.srt / .vtt)
encoding — Source encoding
source — Input format
offsetMs — Offset (integer ms, positive or negative)
negativePolicy — Negative-start policy
format — Output format

Real example

1
00:00:00,500 --> 00:00:02,000
First line
→ 1
00:00:02,000 --> 00:00:03,500
First line
(offset +1500ms)

Limits and failure handling

Offset must be integer milliseconds (1.5 is rejected). Negative starts are refused by default rather than silently clipped; with clamping, start/end are >= 0 and end >= start. Defaults: 5 MiB / 5000 cues; VTT positioning/style may be lost and the original stays downloadable.

FAQ

Does offset change cue duration?

No. Both start and end receive the same integer milliseconds, so duration is unchanged; only clamped cues change duration.

What if a negative offset is rejected?

The error states how many cues would cross zero; switch the policy to "Clamp to 0" and rerun — the result reports the clamped count.

Can I also change format?

Yes. Choose SRT or WebVTT in "Output format"; the shifted cues are serialized accordingly. Default keeps the source format.

Subtitle Format & Timing Toolkit