Local utility · Last updated: 2026-06-10
Caption Quality Checker Guide
Learn how to check subtitle timing, line length, and characters-per-second (CPS) reading speed 100% locally in your browser.
Tool shortcut includedNo data uploadedRuns in browser
Short Answer: The Caption Quality Checker scans your SRT or VTT files locally, highlighting overlaps, long lines, empty cues, and fast reading speeds (Characters Per Second) to ensure video accessibility.
When to use this
Use this subtitle workflow when you need to prepare captions for YouTube, social media shorts, online courses, or films, and want to verify compliance with readability standards without sharing drafts with online converters.
Basic workflow
- Upload or drag-and-drop your SRT or VTT file into the workspace.
- Review the automatically highlighted line-length, duration, and speed errors.
- Edit cues directly in the table to fix overlapping timing or long text blocks.
- Download the cleaned SRT/VTT file or local WebM file to your machine.
Quality and safety notes
- Maintain a maximum line length of 35-42 characters to prevent visual wrapping problems.
- Try to target a reading speed limit of 15-20 characters per second for broad accessibility.
- Ensure short video hooks are positioned clearly and have high contrast ratios.
Frequently Asked Questions
How are reading speed violations calculated?The checker divides the character count of each subtitle block by its duration in seconds. Values exceeding target characters-per-second (CPS) rates are flagged as speed violations.
Can I edit and download files in this checker?Yes. You can edit text strings or duration values in the warning dashboard and download the cleaned SRT or VTT file immediately from your browser.