YouTube Chapter Validator

A browser-only web app for finding what is broken in your YouTube chapter timestamps.

Paste a YouTube video description, optionally add a YouTube video URL, and the app will check common chapter-breaking problems such as formatting mistakes, invalid ordering, missing 0:00, short chapter gaps, and timestamps that go beyond the detected video duration.

Current Status

This project is currently a frontend-only app.

It can:

• Validate pasted chapter timestamps from a video description
• Show line numbers beside the pasted description
• Use an optional YouTube URL to try to read the video duration client-side
• Show the detected duration in the form
• Warn when a timestamp is longer than the detected video length
• Keep validation rules and common mistakes in a separate file

It does not currently:

• Auto-fetch the full YouTube description from the URL
• Reliably check privacy, channel restrictions, or YouTube Studio state
• Use a backend or the YouTube Data API

What It Checks

• The first detected chapter must start at 0:00
• At least 3 chapter timestamps must be present
• Timestamps must be in ascending order
• Each chapter gap must be at least 10 seconds
• Timestamps must use MM:SS or HH:MM:SS
• Each chapter should be on its own line
• There must be a space between the timestamp and the title
• The chapter list cannot exceed 50 entries
• Long titles may be truncated
• Full URLs inside chapter titles are treated as errors
• @mentions, #hashtags, and bare domains inside chapter titles are treated as fragile and shown as warnings
• If the video duration is detected from the URL, timestamps beyond the video length are shown as warnings

Project Files

• index.html: page structure
• styles.css: styling and layout
• app.js: validation logic, duration lookup, and UI behavior
• chapter-rules.js: rules, mistakes, and manual-review notes

Run Locally

Because the app uses JavaScript modules, serve it through a local web server instead of opening the HTML file directly.

Example:

python3 -m http.server 8000

Then open:

http://127.0.0.1:8000/index.html

How The Optional URL Works

If you provide a YouTube URL and click Validate timestamps, the app tries to read the video duration in the browser using the YouTube iframe player API.

That means:

• The URL is useful for duration-based warnings
• The app can display the detected video length after validation
• The app still cannot pull the full video description automatically in this version

Limitations

• Client-side duration lookup may fail depending on browser conditions, network restrictions, embedding limitations, or YouTube behavior
• Some YouTube chapter conditions still require manual checking
• The rules are based on common YouTube chapter requirements plus observed behavior gathered during this project