SRT Timing and FPS Converter

An SRT time shift moves every subtitle earlier or later when the same timing error persists throughout a video. This SRT time shift tool also offers two-anchor linear synchronization and frame-rate scaling for captions whose error grows over time. Open a valid SRT, select the appropriate mode, compare the output text and download the adjusted file. Dialogue is retained while cue numbers and timestamp formatting are rewritten. You must establish the correction yourself: the SRT time shift tool does not listen to the video or automatically match speech.

Choose the right SRT time shift mode

A constant offset and progressive drift are different problems. If captions are always one second late, a single shift can solve that measured offset. If they align near the beginning but become several seconds late later, changing every time by one fixed value will leave part of the file wrong. The two-anchor or FPS modes adjust the timeline scale instead.

Choose Shift only for a uniform error, Two-point sync for two known pairs of original and desired times, or FPS conversion when you have a justified source-to-target playback-rate relationship. Do not assume that two files labeled with different frame rates necessarily need their caption timestamps rescaled: videos may have been re-encoded without changing duration.

Load, adjust and download subtitles

1. Open the .srt with Choose file. Review Text encoding and choose a specific encoding if the previewed words are unreadable.
2. Select the synchronization mode and enter the shift in milliseconds. A positive value delays captions; a negative value advances them.
3. For two-point synchronization, enter the two original anchors and their two desired target times in HH:MM:SS,mmm form.
4. For FPS scaling, enter Original frames per second and Target frames per second.
5. Select Process files, inspect the text preview and download subtitles.srt.

File selection processes with the current values. Rerun after changing a control before downloading. The four anchor controls and two frame-rate controls are present together; only the selected synchronization mode determines which transformation is used. The shift value is additionally applied in all modes.

Example: delay every cue by half a second

For a cue starting at 00:00:01,000 and ending at 00:00:03,500, Shift only with 500 milliseconds produces 00:00:01,500 --> 00:00:04,000. Its duration stays 2.5 seconds, because both endpoints move by the same amount.

With a shift of -500, that source cue starts at half a second. However, a cue starting at 200 milliseconds would become negative. This SRT time shift tool rejects a transformation that produces negative start times instead of silently clipping or deleting the cue. Reconsider the offset or make a deliberate edit to that early caption.

Two anchors and FPS scaling explained

For anchors, the scale is the difference between target times divided by the difference between source times. The offset makes the first original anchor land on its target. If source anchors are 10 and 70 seconds and target anchors are 12 and 78 seconds, the scale is 66/60, or 1.1, and the offset is 1 second before any extra shift.

In FPS mode the implemented scale is original FPS divided by target FPS. A source timestamp of 24 seconds with original FPS 24 and target FPS 25 becomes 23.04 seconds before an extra shift. Millisecond endpoints are rounded. This is a timing transformation, not a change to the video’s frame rate or an analysis of encoded frames.

Limits and practical synchronization checks

Both anchor pairs must increase in time, and FPS values must be positive and no greater than 240. A reversed cue or invalid source timestamp needs correction before scaling. Cuts, advertisements, added scenes and discontinuous edits cannot generally be fixed by one linear formula; those need section-specific work in a subtitle editor.

Check a clearly spoken line near the beginning, middle and end in the actual player. The SRT time shift tool shows subtitle text, not a synchronized video preview, and it cannot tell whether the source refers to another film cut. Keep a backup and use small, measured corrections rather than repeatedly adjusting an already transformed download without a record.

For recoverable numbering or separator problems, use SRT subtitle repair first. For separate caption parts, merge the SRT files with its join rules, then check timing. Finally, convert to WebVTT if the receiving web player requires that format. Each step solves a different problem and does not restore text or timing missing from the original.

Common SRT time shift tool errors and how to fix them

When the SRT time shift tool cannot use a file, it stops with one clear message instead of producing a half-finished download. These are the problems people run into most often, with the fix for each:

• The adjustment creates negative or invalid timing. Increase the shift or correct the anchors. A negative shift would move early cues before 00:00:00,000.
• Both anchor pairs must be in increasing time order. In two-point sync, the second anchor must come after the first.
• A subtitle ends before it starts. A cue has an end time earlier than (or equal to) its start time, often from a typo such as 00:01:05 written as 00:00:65 or swapped times. Correct that cue in a text editor and process the file again.
• Enter valid subtitle times or a finite shift. The shift is empty or not a number of milliseconds.

Privacy: the SRT time shift tool runs in your browser

SRT time shift tool processing happens with JavaScript in a background worker on this page. Your file is not uploaded to a FileFix server, and the results you download are created in your browser’s memory. Unreleased video scripts and captions stay on your computer. When you finish on a shared computer, clear the selection or close the tab.

For the underlying format rules, see the Library of Congress description of SubRip (SRT). The SRT time shift tool follows the subset described on this page rather than every optional feature in those documents.

Sources

• Library of Congress description of SubRip (SRT)

Questions about this tool