Subtitle Quality Checker
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
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.
Subtitle Quality Checker 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.
Broadcast Delivery
Review reading speed, line length, and timing against your delivery thresholds before sending subtitles to TV networks.
Streaming Platforms
Validate subtitle quality before uploading to streaming platforms or video hosts.
Professional QA
Quality-check subtitle files during the translation and post-production QA process.
Accessibility Compliance
Use readability and timing checks while preparing closed captions for accessibility review.
Translation Review
Check translated subtitles for readability issues like excessive reading speed or overly long lines.
How It Works
Streamlined end-to-end processing pipeline engineered for speed and precision.
Upload & Import
Upload your subtitle file.
Format Analysis
The tool parses all cues and calculates metrics for each one.
Configuration
Each cue is checked against configurable quality guidelines: CPS thresholds, line length, duration limits, and timing gaps.
Processing
Review the quality score and detailed issue list with severity levels.
Verify & Export
Fix issues in your subtitle editor and re-check.
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
CPS measures reading speed — how many characters appear per second of subtitle display. Common guidelines recommend around 20 CPS for comfortable reading, with values above 25 flagging subtitles that may be difficult for viewers to follow in fast dialogue.
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.
Many delivery specs use a maximum around 42 characters per line, but the checker's thresholds are configurable. Longer lines may wrap unpredictably or overflow on some devices.
Yes. Everything runs client-side. No subtitle data is ever sent to a server.
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