Step 1 / source
Add the source media
Source intake
Drop one media file here
Choose the subtitle track that is consistently early or late by the same amount.
UTF-8 SRT or VTT1 subtitle / 2 MB
Checking publication status before file selection...
TEMPORARY MEDIA WORKSPACE / SUBTITLE TIMESTAMP SHIFTER
Subtitle Timestamp Shifter
Move every valid SRT or VTT cue earlier or later by one signed offset while preserving each cue duration and clamping negative starts to zero.
Request-scoped temporary processingAdd one UTF-8 SRT or VTT file up to 2 MB containing no more than 10,000 valid, ordered subtitle cues.No account required
Local API readinessMedia service ready
One bounded job runs per API worker by default.The processor required by this tool is available, and this worker can accept a temporary job.
1 subtitle / 2 MB
Temporary server workspace
The selected bytes are sent only to the Nirmion media API for this request. Processing uses a private temporary workspace rather than permanent catalogue storage.
Request-scoped cleanup
Server-side source and result files are removed when the response stream closes. Re-downloads use the result Blob retained only in this browser tab.
Original stays unchanged
Nirmion writes a separately named result containing nirmion_tools and never overwrites the selected source file.
Know the product contract
What goes in, what changes, what comes back
Every media page documents the accepted source, the selected FFmpeg transformation, the output container, and the limits that can affect the job.
Prepare the source
Measure the same sync error at several points. A growing mismatch indicates drift and cannot be fixed by one constant offset.
Apply one operation
The parser validates every cue, applies the signed millisecond offset, preserves cue duration, and serializes normalized SRT or VTT.
Receive a separate file
Test the beginning, middle, and end against the exact video version before publishing.
Plain-language method
How global subtitle shifting works
A fixed offset corrects consistent delay only. It does not stretch timing, identify speech, translate text, or repair frame-rate drift.
- 01Choose valid source media
Measure the same sync error at several points. A growing mismatch indicates drift and cannot be fixed by one constant offset.
- 02Review the operation settings
Enter 2.5 when subtitles should appear later by two and a half seconds, or -2.5 when they should appear earlier.
- 03Inspect and download the result
Test the beginning, middle, and end against the exact video version before publishing.
Useful when
Practical jobs this tool handles
- Correct subtitles exported with a delayed start.
- Align captions after a fixed intro was removed.
- Prepare a synchronized review track.
Before processing
Check the source and output choices first
- Confirm the error is constant.
- Use the correct positive or negative sign.
- Retain the source subtitle.
- Spot-check three timeline positions.
Container and codec
Understand the output format
The source format is preserved. VTT cue settings are accepted but normalized timing output does not preserve unsupported STYLE or REGION blocks.
Know the boundary
One offset cannot correct progressive drift
If captions gradually move out of sync, a constant shift will only align one point. Use a retiming workflow that can scale or remap timestamps across the full program.
Quick answers
Questions before you process media
These answers describe the actual upload, FFmpeg processing, download, and temporary-retention contract.
What does a positive value do?
It delays every cue.
Can a cue become negative?
No. Starts are clamped to zero while cue duration is preserved.
Does this change caption words?
No. Cue text is retained.