youtube_section_repeat

Section Repeat for YouTube™

Project Status: 🟢 Active

Type: 🧩 Chrome Browser Extension

1. Overview

The ultimate tool for musicians, dancers, language learners, and anyone who needs to master specific parts of a video.

Section Repeat for YouTube™ is a browser extension engineered to enhance practice and learning efficiency on the YouTube platform. It provides a keyboard-driven interface for slicing and repeating of video segments. It enables A-B repeat style practice by looping user-defined clips, prioritizing a streamlined, mouse-free experience for music, dance, and language learning.

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2. Core Principles

This extension is built on three core principles:

• 🔒 Privacy First: We do not collect, store, or share any of your personal data. Everything happens on your computer, and we have no access to your viewing history or activity.
• ⚡️ Performance-Oriented: Built with modern Manifest V3 standards and VanillaJS, the extension is designed for minimal impact on browser resources. It is lightweight and fast, with no external frameworks.
• ⌨️ Keyboard-Centric: All core functions are designed to be controlled entirely without a mouse, allowing you to stay focused on your practice without interrupting your workflow.

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3. Key Features

• Precision Slicing: Define multiple, high-precision video sections with a single key press.
• Keyboard-Centric Workflow: All core functions are mapped to intuitive hotkeys (S, E, R, A, D, Q, 1-9) for maximum efficiency.
• Seamless Navigation & Repeat: Instantly navigate sections with A/D and toggle repeat mode with R.
• Auto-Looping: When a video with defined sections ends, repeat mode automatically starts from the first section.
• Focus Mode: A dedicated “Focus Mode” (W key) reloads a video from a playlist into a standalone player, preventing auto-play from interrupting your repeat sessions.
• Direct Section Access: Instantly jump to the first nine sections using the number keys 1-9.
• Intelligent Error Prevention: Incomplete sections are automatically completed if long enough or discarded if too short, ensuring a seamless transition into repeat mode.

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4. Getting Started

Installation

1. From the Chrome Web Store (Recommended)

• Install Here

2. Manual Installation (for Developers)

Click to view installation instructions

1. Clone this repository or download and unzip the source code. 2. Open Chrome and navigate to `chrome://extensions`. 3. Enable "Developer mode" in the top-right corner. 4. Click "Load unpacked" and select the project's root directory.

Quick Start

1. Make a section: Press S to start, E to end.
2. Chain sections: Press E again to add the next section.
3. Repeat & Navigate: Press R to repeat. Press A or D to jump between sections.

Basic Usage

Key	Action	Description
S	Start section	Sets the start-time for a new section.
E	End (Chain) section	Completes the current section. Press again to start the next section where the last one ended (chaining).
R	Toggle Repeat	Starts or stops repeating through the defined sections.
Q	Clear all sections	Deactivates all extension functions and clears all sections for the current video.
W	Enter Focus Mode	In a playlist, reloads the video in a standalone view to prevent auto-advancing.
A/D	Previous / Next section	Moves to the previous (A) or next (D) section and begins repeating automatically.
1-9	Jump to section	Instantly jumps to a specific section (1 through 9).

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5. Technical Architecture

• Core Logic: Vanilla JavaScript, compliant with the Manifest V3 standard.
• State Management: The background service worker (background.js) manages tab states and global settings, using chrome.storage.session for non-persistent data and chrome.storage.sync for user preferences.
• DOM Interaction: A single, unified MutationObserver monitors the YouTube player, with debouncing and filtering to minimize performance impact. DOM lookups are optimized via an LRUCache.
• UI Components: Toasts and overlays render in isolated Shadow DOM trees to prevent style conflicts with the host page.
• Security: Locally stored video IDs are hashed with a device-specific salt using the SubtleCrypto API. The extension makes no external network requests.

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6. Technical Specifications

• Section & Storage Limits:
  • Max Sections per Video: 50
  • Min Section Duration: 0.5 seconds
  • Data Expiration: Sections unused for 30+ days are subject to cleanup.
  • Max Total Keys: 3,000
  • Storage Quota: 5MB (chrome.storage.local)
• Storage Cleanup:
  • Automatic Purge: Runs every 60 minutes to clear expired data.
  • User Notifications: A toast notification is shown when storage usage exceeds 75%, and a manual cleanup button appears in the popup when usage exceeds 90%.

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7. Project Information

• Author: Eunjeong Song (Homepage / LinkedIn)
• Source Code: https://github.com/songej/youtube_section_loop
• Privacy & Legal:
  • Privacy Policy: Read our Privacy Policy
  • License: This project is licensed under the PolyForm Noncommercial License 1.0.0. This software may be used, copied, modified, and distributed for noncommercial purposes only.
  • Disclaimer: Section Repeat for YouTube™ is an independent project and is not officially associated with YouTube or Google LLC. “YouTube” is a trademark of Google LLC.
• Acknowledgements: Icon by khulqi Rosyid from IconFinder (CC BY 4.0).

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