Tools in This Collection
Subtitle Synchronization Workflow
Out-of-sync subtitles are the most common subtitle problem. The cause is usually a mismatch between the subtitle file and the video encode — different release versions of the same film, streaming vs Blu-ray timing differences, or frame rate mismatches between PAL (25fps) and NTSC (23.976fps) versions. Both tools here run in your browser on SRT files.
Fixing a Constant Offset
If your subtitles appear consistently early or late throughout the entire video — for example, every subtitle appears exactly 2.5 seconds before the dialogue — use the Subtitle Time Shifter. Enter the offset in milliseconds (positive to delay, negative to advance) and the tool applies it to every cue. A common workflow: find a cue you know the exact timing for, measure the difference between when it appears and when it should, and use that difference as your shift value.
Fixing Progressive Drift
Progressive drift is harder to fix: subtitles start roughly in sync but gradually fall further out of sync as the video progresses. By the end of a 2-hour film, subtitles that were 1 second off at the start may be 5-8 seconds off. This is typically caused by a frame rate mismatch — a subtitle file timed for 23.976fps playing with a 25fps video encode, or vice versa. Use the Partial Subtitle Shifter for this: specify two sync points (a cue number where timing is correct and one where it's wrong), and the tool applies linear interpolation to gradually correct the offset across all cues in between. This corrects progressive drift without manually editing each cue.
Frequently Asked Questions
How do I find the correct time offset to fix my subtitles?
Pause the video on a line of dialogue you can recognize, note the video timestamp. Find that same cue in your subtitle file and note its timestamp. The difference (video time minus subtitle time) is your offset. If the subtitle shows at 00:02:10 but the dialogue happens at 00:02:12.5, shift by +2500 milliseconds.
What causes progressive subtitle drift?
Progressive drift is almost always caused by a frame rate mismatch. Subtitle files timed for 23.976fps (NTSC) will drift when played with a 25fps (PAL) video encode, and vice versa. A 1-hour film at 25fps has 90,000 frames; at 23.976fps it has 86,313.6 frames. The 4% difference accumulates to several seconds of drift by the end.
Can I fix subtitles that have both a constant offset and progressive drift?
Yes, but it requires two passes. First use the Subtitle Time Shifter to correct the initial offset (the amount off at the start of the video). Then use the Partial Subtitle Shifter to correct the remaining drift that accumulates toward the end. After the first pass, the drift becomes a scaling problem rather than a constant-offset problem.