YouTube Live Chat Fullscreen

English (US) · 日本語 · 繁體中文 (台灣)

Keep YouTube Live in fullscreen and keep chatting without layout compromises.

Install on Chrome · Install on Firefox · Star on GitHub

Why This Extension

• Watch streams in true fullscreen while still reading and sending chat messages.
• Drag and resize the chat overlay so it fits your stream setup, game HUD, or subtitles.
• Improve readability with chat style controls (background, font, blur, spacing, and more).
• Save and switch presets for different viewing contexts.
• Works with both live streams and archives that have chat replay.

30-Second Quick Start

1. Install from the Chrome Web Store or Firefox Add-ons.
2. Open a YouTube live stream, or an archive video with replay chat.
3. Enter fullscreen and toggle chat from the switch at the bottom-right.
4. Drag/resize the overlay and tune styles from the extension settings.

Mode Behavior (Live / Archive / No Chat)

Video state	Chat source used by extension	Switch / Overlay
Live stream	Public live_chat?v=<videoId>	Available
Archive with replay chat	Native live_chat_replay iframe	Available when replay is playable
No chat / replay unavailable	None	Hidden

Preview

Key Features

• Fullscreen chat posting, including Super Chat posting flow.
• Overlay drag, resize, and position control.
• Visual customization: background color, font color, font family, font size, blur, spacing.
• Display toggles: username, user icon, Super Chat bar, and chat-only view.
• Preset management for quick style switching.
• Multi-language support.

Download

• Chrome Web Store
• Firefox Browser Add-ons

Development Setup

Requirements

• Node.js (v22.x)
• Yarn (via Corepack recommended)

Install

git clone https://github.com/daichan132/Youtube-Live-Chat-Fullscreen.git
cd Youtube-Live-Chat-Fullscreen
corepack enable
yarn install

Commands

• yarn dev: Start development server.
• yarn dev:firefox: Start development server for Firefox.
• yarn build: Build the project.
• yarn build:firefox: Build for Firefox.
• yarn zip: Create a zip package.
• yarn zip:firefox: Create a Firefox zip package.
• yarn lint: Run Biome checks and TypeScript type checks.
• yarn test:unit: Run unit tests.
• yarn storybook: Launch Storybook.
• yarn storybook:build: Build static Storybook output.
• yarn e2e: Run end-to-end tests.

In Storybook, open Catalog/CurrentUIDesigns to review the current UI design in one place.

Quality Checks

Run these before opening a pull request:

yarn lint
yarn test:unit
yarn build

For Firefox compatibility changes, also run:

yarn build:firefox

Project Overview

This extension uses a content script to control fullscreen chat behavior on YouTube pages. Popup settings (language, on/off, theme) are synced with content runtime state.

Contributing

Contributions are welcome. If you have ideas, bugs, or improvements:

• Open an issue or submit a pull request.

Support

If this extension improves your YouTube workflow, starring this repo helps a lot.

• Star this repository
• Support on Ko-fi

License

Licensed under GPL-3.0. See LICENSE for details.

Translations

• English (US): README.md
• 日本語: README.ja.md
• 繁體中文 (台灣): README.zh-TW.md

Contributions for additional languages are welcome. Follow the same filename pattern: README.<locale>.md.