Subtitle Tools

Shift Subtitle Timestamps

Shift Subtitle Timestamps corrects a consistent synchronization delay by adding the same offset to every SRT or WebVTT cue. Use a positive value when captions appear too early and need to move later; use a negative value when they appear too late and need to move earlier. It cannot repair drift that grows over time, which requires scaling or retiming.

Runs locally — files stay on your device

Input

Offset in seconds

Quick answer

How do I synchronize subtitles with a fixed delay?

Enter the offset in seconds and apply it to every cue. Positive offsets move subtitles later; negative offsets move them earlier.

A timestamp shift changes position, not duration

Adding a fixed offset moves each cue's start and end by the same amount. Cue duration and spacing remain unchanged. This solves a constant delay but not a frame-rate mismatch or progressive drift.

How it works

Find a clearly spoken event and measure how many seconds separate the sound from its caption. Apply that offset, then check cues near the beginning and end. If one end aligns but the other does not, a uniform shift is the wrong correction.

Key concepts

Choosing the offset direction

If the subtitle appears before the matching sound, move it later with a positive offset. If it appears after the sound, move it earlier with a negative offset.

Constant delay versus drift

Constant delay stays the same throughout. Drift changes progressively and usually points to speed, frame-rate, or source-version differences.

When to use it

Correct subtitles that are consistently early by the same amount.
Move captions earlier after a fixed lead-in was removed from a video.
Create an alternate synchronized copy while preserving cue durations.

When not to use it

Do not use a fixed shift for drift that increases during playback.
Do not allow negative timestamps at the beginning.
Do not assume one measured cue proves alignment across the entire program.

Worked examples

Captions appear two seconds early

Input: Offset = +2.0 seconds
Expected output: Every cue starts and ends two seconds later

The positive shift delays the complete subtitle schedule.

Video intro removed

Input: A 5.5-second intro was cut; offset = -5.5
Expected output: Cues move 5.5 seconds earlier

The timing is aligned with the shortened video.

Progressive drift

Input: Aligned at minute 1 but ten seconds late near the end
Expected output: No single offset fixes both positions

A timing-scale or source-version correction is required.

Common mistakes

Reversing the offset sign

The subtitle moves farther from the matching sound. Correction: Use positive to move later and negative to move earlier.

Creating negative cue times

A large negative shift can push opening cues before zero. Correction: Inspect the first cue and reduce or manually handle the opening offset.

Using shift to fix drift

The error changes across the running time. Correction: Use a retiming tool that can scale or anchor the subtitle schedule.

Best practices

Measure offset against a clear sound or spoken consonant.
Check synchronization near the start, middle, and end.
Save shifted output as a new file and retain the source.

Limitations and privacy

Only a constant offset is applied.
Cues pushed before zero may need special handling.
The tool does not change subtitle speed, wording, or video duration.

Subtitle text is transformed locally in this browser and is not uploaded to Toolbox.

Frequently asked questions

Should I use a positive or negative subtitle offset?

Use positive to move captions later and negative to move them earlier.

Does shifting change how long cues stay visible?

No. Start and end move together, so duration stays the same.

Can this fix subtitles that drift gradually?

No. Progressive drift requires timing-scale or frame-rate correction.

What happens to cues moved before zero?

They cannot play before the media starts and may need manual adjustment or removal.

References

W3C WebVTT specification