Auto
Combine fragmented subtitles from Whisper and YouTube into clean, readable cues. Stop the rapid-fire flashing of one-word subtitle blocks.
Drag & drop your subtitle file here
Drag and drop subtitle files here or click to browse
What the Auto-Merger Does
Engineered for video editors and localization teams. Helps enforce common subtitle timing rules and formatting.
Auto 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.
Who Needs Auto-Merging?
Real-world scenarios across video post-production, course transcription, and global localization.
Whisper & AI Transcription
AI transcription tools fragment speech into tiny one-word cues that flash rapidly. Merge them into natural sentences automatically.
YouTube Auto-Captions
YouTube's automatic subtitles break text into very short blocks. Combine them for a smooth reading experience before publishing.
Post-Production Editing
Before editing or translating, merge fragmented cues so you work with complete sentences instead of fragments.
Accessibility & Reading Comfort
Rapid single-word subtitles are hard to read. Merging improves comprehension for all viewers.
How It Works
Streamlined end-to-end processing pipeline engineered for speed and precision.
Upload & Import
Upload your subtitle file (especially effective on Whisper or YouTube output).
Set the merge thresholds
max characters per line, pause threshold, and max merged duration.
Configuration
The merger scans for adjacent cues with short gaps and combines them greedily.
Processing
Each merge only happens if the combined text fits the character limit and duration cap.
Verify & Export
Download the cleaned subtitle file with natural, readable cue blocks.
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
AI transcription tools like Whisper and YouTube auto-captions generate very short cues, often one or two words each, with tiny gaps between them. This causes rapid flashing on screen and poor readability.
No. Cues separated by pauses longer than your threshold are never merged. This preserves natural breaks where the speaker actually paused.
Input: SRT, VTT, ASS, SSA, LRC, SBV, TTML, SCC, STL, SMI. Output: SRT.
It merges adjacent cues only when three conditions are met: the gap between them is shorter than your pause threshold (default 400ms), the combined text fits your character limit (default 35), and the merged duration stays under the maximum (default 5 seconds).
Only minimally. The merged cue keeps the first cue's start time and takes the last merged cue's end time. The on-screen timing stays accurate to the original speech.
Yes, completely free with no sign-up or limits. It runs entirely in your browser.
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