Partial Subtitle Sync
Fix subtitles that start in sync but drift partway through. Adjust only the cues you need without touching the rest.
Drag & drop your subtitle file here
Drag and drop subtitle files here or click to browse
Key Features
Engineered for video editors and localization teams. Helps enforce common subtitle timing rules and formatting.
Partial Subtitle Sync Live Execution Demo
In-Memory Processing
File parsing, mutations, and time shifts for standard tools run in browser memory without sending subtitle files to our servers.
Millisecond Precision
Millisecond-accurate timecode parsing and arithmetic prevent synchronization drift across desktop and web players.
Fault-Tolerant Engine
Automatic multi-encoding detection and syntax sanitization gracefully handle malformed cues and unexpected linebreaks.
Common Use Cases
Real-world scenarios across video post-production, course transcription, and global localization.
Post-Credits Drift
Subtitles are perfectly synced at the start but gradually drift out of sync after the midpoint. Adjust only cues from the drift point onward.
Inserted Scene
A scene was inserted or removed mid-video, pushing all subsequent subtitles out of sync. Shift only the cues after the edit point.
Act Break Correction
TV episode subtitles have a gap for ad breaks in one version but not another. Fix the timing offset for cues after each break.
Section-Specific Fix
Only a portion of the subtitles needs correction while the rest are already accurate. Target only the affected range.
Chapter Realignment
Realign subtitle timing for a specific chapter or scene without disturbing the rest of the file.
Partial Speed Correction
A portion of the video was sped up or slowed down. Use two-point calibration within that range to match the new timing.
How It Works
Streamlined end-to-end processing pipeline engineered for speed and precision.
Upload & Import
Select your subtitle file that has a sync issue in a specific section.
Format Analysis
Enter the start and end cue numbers for the range that needs adjustment.
Configuration
Choose Time Shift for a fixed offset, or Two-Point Calibration for speed/drift correction within the range.
For Time Shift
enter how much to delay or advance the selected cues.
For Two-Point
enter the current and correct timestamps for two reference cues within the range.
Delivery
Click Sync and download the corrected subtitle file.
Why Choose AllSubConverter?
Client-Side Privacy
Standard tools run in your browser so standard files are not uploaded to our servers.
Fast Local Parsing
Optimized processing engine parses and converts files directly in your browser.
Generous Batches
Up to 50 MB per file, 200 files or 1 GB total per batch.
Universal Compatibility
Runs in modern browsers across Windows, macOS, Linux, iOS, and Android.
More Subtitle Tools
Frequently Asked Questions
Regular subtitle sync adjusts ALL cues in the file. Partial sync lets you specify a start and end cue number, so only cues within that range are adjusted while the rest remain exactly as they were.
Open your subtitle file in a text editor. Each cue starts with a number (1, 2, 3...). Enter the number of the first cue that needs adjustment as the start, and the last cue that needs adjustment as the end.
Cues before the start index and after the end index are left completely unchanged. Their timing and text are preserved exactly as in the original file.
Use partial sync when subtitles are correct for part of the video but drift out of sync after a certain point. This is common when a scene was added or removed, or when the subtitle file has a different version of the second half.
Yes. Select Two-Point Calibration mode and provide two reference cues within your selected range. The tool calculates a linear transformation that is applied only to cues in that range.
Input: SRT, VTT, ASS, SSA, LRC, SBV, TTML, SCC, STL, SMI. Output: SRT or VTT.
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