Subtitle Quality Checker
Fast. Private. Perfect.
Analyze subtitles for CPS, line length, overlaps, timing gaps, and more. Get an instant quality score with detailed issue reports.
Drag & drop your subtitle file here
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SRT, VTT, ASS, SSA, LRC, SBV, TTML, SCC, STL, SMI, TXT
How It Works
Upload your subtitle file.
The tool parses all cues and calculates metrics for each one.
Each cue is checked against broadcast quality standards: CPS thresholds, line length, duration limits, and timing gaps.
Review the quality score and detailed issue list with severity levels.
Fix issues in your subtitle editor and re-check.
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
Broadcast Delivery
Ensure subtitles meet broadcast standards for reading speed, line length, and timing before delivery to TV networks.
Streaming Platforms
Validate subtitle quality before uploading to Netflix, Amazon Prime, YouTube, or other streaming platforms.
Professional QA
Quality-check subtitle files during the translation and post-production QA process.
Accessibility Compliance
Verify that subtitle timing and text meet accessibility guidelines for closed captions.
Translation Review
Check translated subtitles for readability issues like excessive reading speed or overly long lines.
Frequently Asked Questions
CPS measures reading speed - how many characters appear per second of subtitle display. Broadcast standards recommend a maximum of 20 CPS for comfortable reading. CPS above 25 is considered critical and may be too fast for viewers to read.
Overlapping cues happen when one subtitle starts before the previous one ends. This can cause display issues on some players. Check your timing and adjust using the Subtitle Sync or Subtitle Editor tools.
Yes, completely free with no registration, no watermarks, and no file uploads.
A score of 80-100 is good (minor issues only). 60-79 indicates several warnings that should be reviewed. Below 60 suggests significant problems that need fixing. Errors (overlaps, very high CPS) have the highest impact on the score.
The industry standard is a maximum of 42 characters per line. Lines longer than this may wrap unpredictably or overflow the screen on some devices.
Yes. Everything runs client-side. No subtitle data is ever sent to a server.