Professional Subtitle Synchronization
Instant correction of audio-subtitle offsets
Supports standard SRT (SubRip) files
100% local processing - maximum privacy
No installation, no subscription, completely free
# Perfect SRT Subtitle Synchronization
There is nothing more frustrating for a viewer than seeing dialogues that do not match the voices. Subtitle offset usually occurs due to differences between video versions: variations in framerate, advertising cuts, production intros, or changes in compression. With this tool, you fix the problem in seconds. 100% Local Processing
Milliseconds Precision
Any Size NO File Limit
# Advance vs Delay: Practical Guide
The first step is to correctly identify the type of offset. Here is the logic:- Delay (Positive Value): When you see text appear BEFORE the sound. Subtitles are ahead. Example: +2.0 seconds.
- Advance (Negative Value): When you see text appear AFTER the sound. Subtitles are behind. Example: -2.0 seconds.
- Test and Adjust: Start with small increments (0.5s) and use the preview to validate.
Professional Level Privacy
By processing the file via client-side JavaScript, we guarantee that your subtitle content never leaves your computer. Essential for translators and professionals handling confidential material or under NDA.
# Common Use Cases
Translators and Subtitlers
Synchronize translations after working with multiple video versions
- SRT files from different sources
- Content versioning (theatrical vs streaming)
- Fast delivery without changing tools
Content Creators
Recover subtitles when video was processed with different framerate
- Reuse existing subtitles
- Format changes (720p to 1080p)
- Avoid manual retiming of 1000+ lines
Casual Users
Correct downloaded subtitles that don't fit perfectly
- Generic out-of-sync subtitles
- Movies in different region (PAL vs NTSC)
- Streaming with edited versions
# Why Subtitles Go Out of Sync
| Common Cause | Technical Description | Solution |
|---|---|---|
| Framerate Difference | 23.976 fps vs 25 fps - accumulated difference | Single offset adjustment (this tool) |
| Editorialization | Ad cuts or additional content removed | Manual calculation + synchronization |
| Regional Version | PAL (25 fps Europe) vs NTSC (29.97 fps USA) | Simple mathematical offset |
| Resolution Change | Re-encoding with different processing speed | Recalculation of original file |
Technical Limitations to Consider
This tool applies a constant offset to the entire file. If the offset is progressive (starts well but gradually goes out of sync), it indicates a persistent framerate difference. In that case, the original file needs re-processing in professional editing software.
Advantages
- Extreme speed - processes large files in milliseconds
- Total privacy - content never leaves your browser
- Universal format - works with any standard SRT
- Completely free, no advertising, no tracking
Limitations
- Only adjusts fixed offset, not progressive ones
- Requires modern browser with JavaScript enabled
- Does not support other formats (ASS, VTT, SCC, etc.)
- No change history or versioning
- SRT (SubRip)
- Most universal subtitle format: text file with sequence numbers, times (hh:mm:ss,mmm), and text. De facto standard in players and platforms.
- Offset
- Fixed amount of time added or subtracted from all times in the file. Can be positive seconds (delay) or negative (advance).
- Framerate (fps)
- Frames per second. 24p (cinema), 25p (PAL/Europe), 29.97p (NTSC/USA), 60p (fluid video). Differences cause cumulative offsets.
- NTSC vs PAL
- Regional television standards: PAL (25 fps) in Europe; NTSC (29.97 fps) in USA. ~4% speed difference.
- Progressive Offset
- When synchronization starts correct but ends up gradually out of sync. Indicates persistent framerate difference, requires re-processing.
Professional Editing with Full Control
Our approach is simple but powerful: a single offset, applied instantly, processed 100% in your browser. No cloud, no storage, no tracking. Simply upload, adjust, download. Full control over your content.