Delay SRT by 1.25 seconds
Input and settings
1 00:00:01,000 --> 00:00:02,250 Hello Offset: +1.250 s; SRT
Expected result
1 00:00:02,250 --> 00:00:03,500 Hello
SRT / VTT Subtitle Time Shift
Shift SRT/VTT cue times together while preserving text, settings and line endings. Save adjusted subtitles as UTF-8.
How to use
- Enter subtitles or choose a subtitle file.
- Choose the subtitle format and time offset, then adjust times.
- Review the resulting times and any errors, then save the subtitles.
Subtitles and offset
Choose one UTF-8 SRT/VTT file or paste text below.
Positive offsets delay cues; negative offsets make them earlier. Up to three decimal places, ±86,400 seconds. UTF-8 only, 2 MB, 1,000,000 UTF-16 units and 20,000 cues.
Adjusted subtitles
How to use and supported formats
Enter an offset in seconds. For example, 1.250 delays every cue by 1 second and 250 ms; -0.500 makes cues 500 ms earlier. Start and end times move together, preserving durations, order and existing overlaps. Formats are not converted and text is not edited.
The entire operation is rejected if any shifted time is negative or exceeds 99:59:59.999, or if an end time is not later than its start. Times are not clamped to zero. SRT needs standard numeric-index, timing and text blocks; VTT needs a WEBVTT header, timing and text. Separate cues with blank lines.
SRT commas, VTT dots, text, identifiers, timing settings, NOTE/STYLE/REGION blocks, line endings and a UTF-8 BOM are preserved. Hours are added to short VTT timestamps only when required. X-TIMESTAMP-MAP, other encodings, encrypted files and video/audio inputs are unsupported.
Only cue timing lines change. Timestamp-like text inside cue bodies is unchanged. Subtitle HTML/CSS is never executed or rendered. Check the saved file in your player. Changes or cancellation discard the old result. Input, filenames and output are neither stored nor sent.
Try a use case and check the result
Shift all subtitle timestamps by a fixed offset while retaining cue text and durations.
Trying an example replaces the input and settings and runs the tool above. Restore previous input restores the preceding input and settings, not a saved copy of the calculated result; run again as needed. Existing storage rules apply.
After trying multiple examples, repeat Restore previous input to return to your original input. History is kept only in this page; restore any input you need before closing it.
Advance VTT by half a second
Input and settings
WEBVTT 00:01.000 --> 00:02.000 Hello Offset: -0.500 s; VTT
Expected result
WEBVTT 00:00.500 --> 00:01.500 Hello
How to read the result
Positive offsets delay cues and negative offsets advance them. Moving both endpoints equally preserves duration. Timestamp-looking text in cue content is not replaced. Saving the result does not change the original file.
Scope and limits
Only UTF-8 SRT/VTT is supported. Offsets allow three decimal places within ±86,400 seconds. Negative shifted times, times beyond 99:59:59.999, and nonpositive cue durations are rejected. Input limits are 2,000,000 bytes, 1,000,000 UTF-16 code units and 20,000 cues. Video analysis and automatic synchronization are not provided.
Verification: millisecond offsets and preserved cue text from the existing shift function are compared with Worker-based browser output. Examples wait until existing processing is idle.
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Frequently asked questions
Does subtitle text change?
Text and non-timestamp settings are preserved.
What if a cue becomes negative?
The whole operation is rejected. Adjust the offset.
Does it analyze a video to infer the synchronization offset?
It does not analyze video or infer synchronization. It applies your chosen offset to UTF-8 SRT/VTT subtitles.
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Inputs and storage
Keep any content you need before clearing. This tool does not autosave inputs or results. Reloading or closing the page, clearing inputs or resetting may discard your work.
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