Multi-Screen YouTube Danmaku Viewer

Show multiple YouTube videos/streams in a grid with Niconico-style danmaku comments and chat.

Watch several YouTube videos or live streams side by side in a single grid, each with Niconico-style "danmaku" scrolling comments and a chat list overlaid. Features: - Add tiles by pasting a YouTube URL or video ID; add as many as you like - Stream live/archived chat as danmaku over each video (Niconico style); Super Chats and membership badges shown too - Post comments to each stream (using your signed-in YouTube account) - Adjust danmaku font, size (up to 128px), opacity, speed, outline, and max lanes for all tiles at once - Control playback speed (0.5x-2x), master volume, mute, and video quality (auto/highest/high/medium/low) across all tiles; per-tile volume too - Time-sync archived streams to real time; play all / seek / scrub them together - One-click add: a "+" button on each video card, an "Add to viewer" button in the watch-page action row - Volume, speed, quality, and display settings are saved and restored next time - Tiles auto-fit the window (portrait videos get narrow tiles; leftover space is filled to maximize size). Drag a tile's title bar to reorder. - Built-in help in the gear (⚙) menu — a full feature guide in 5 languages - 5 UI languages (Japanese / English / Chinese Simplified / Chinese Traditional / Korean; auto-detect + manual switch) How to use: 1. Click the extension icon in the toolbar to open the viewer. 2. Paste a YouTube URL or video ID in the top bar and click "Add" — or add in one click with the "+" button on each video card, or "Add to viewer" in the watch-page action row. 3. Use the top bar to adjust danmaku (font, size, speed, opacity) and volume / video quality for all tiles at once; per-tile volume, mute, and solo are also available. 4. To line up archives, use "🕐 Sync" to align them to real time so multiple POVs play in perfect sync. 5. (Optional) To post comments, sign in to YouTube in settings, then type in any tile's chat box. Compatibility & price: - Works only on YouTube (youtube.com). Twitch, Niconico, etc. are not supported. - Google Chrome and other Chromium-based browsers. - Completely free — no account or payment required. Privacy: No personal data is collected or sent anywhere. Display settings are stored only on your device. The cookies permission is used solely to post chat as yourself with your signed-in YouTube account, and is never sent to the developer or any third party. FAQ: Q. No danmaku (comments) appear. A. That stream may have chat replay turned off. Try a live stream, or an archive with chat replay enabled. Q. Do I need to sign in? A. Not for watching or danmaku — sign-in is only required to post comments. Q. Does it work on Twitch or Niconico? A. This extension is YouTube-only. Q. Some videos won't display. A. Videos that disallow embedding cannot be shown. Great for following multiple streams at once or watching collab streams with danmaku. Note: Chat retrieval depends on YouTube's internals and may break if YouTube changes.