Subtitle Diff Tool
Fast. Private. Perfect.
Upload two subtitle files and instantly see what changed. Word-level highlighting, timing differences, and an overall similarity score.
Drag & drop your subtitle file here
or click to browse
SRT, VTT, ASS, SSA, LRC, SBV, TTML, SCC, STL, SMI, TXT
How It Works
Upload both versions of your subtitle file.
The tool parses both files and aligns cues by timecode.
Each aligned pair is compared word by word using a diff algorithm.
Review the similarity score and the highlighted differences.
Download the diff report or adjust comparison options and re-run.
Why Choose AllSubConverter?
Your Privacy Matters
Everything runs in your browser. Your files are never uploaded.
Lightning Fast
Optimized processing engine converts files in seconds.
Truly Unlimited
No file size limits. No daily limits. Completely free.
Works Everywhere
Works on Windows, Mac, Linux, iOS, Android - any modern browser.
Key Features
Common Use Cases
Translation QA
Compare original and revised translations to verify that only intended changes were made.
Version Control
Track what changed between two subtitle file versions before committing or delivering.
Collaboration Review
When multiple editors work on the same subtitles, diff shows each person's changes at a glance.
Auto-Caption Verification
Compare machine-generated captions against a corrected reference to measure accuracy.
Frequently Asked Questions
A subtitle diff compares two subtitle files and highlights every difference: lines that were added, removed, or modified. It works like a code diff but for subtitle text and timing.
Tolerance (in milliseconds) controls how close two cues' timecodes must be for them to be considered the same line. A higher tolerance matches more aggressively across versions with timing shifts.
Yes, completely free with no registration, no watermarks, and no file uploads.
The score is based on the ratio of identical cues to total cues after alignment. Modified lines reduce the score proportionally to how many words changed within each cue.
Yes. The tool auto-detects each file's format independently. You can compare an SRT against a VTT, for example.
Yes. Everything runs client-side. No subtitle data is ever sent to a server.