Getting Started

Subtitle Insights relies on experimental Chrome built-in AI APIs. Follow these steps to set up your environment and install the extension.

Prerequisites

• Chrome Version: You must use Chrome 138 or higher.
• Hardware: For specific hardware requirements and supported devices, please refer to the official Chrome Prompt API documentation.

1. Enable Chrome Flags

You must enable several experimental flags to allow local AI processing:

1. Open chrome://flags in your browser.
2. Search for and Enable the following flags:
   • #optimization-guide-on-device-model (Set to Enabled BypassPrefocals)
   • #prompt-api-for-gemini-nano (Set to Enabled)
   • #translation-api (Set to Enabled)
3. Relaunch Chrome.

2. Install the Extension

The easiest way to install Subtitle Insights is by downloading a pre-built version from the releases page.

Option A: Install from GitHub Releases (Recommended)

1. Navigate to the Releases page on GitHub.
2. Download the subtitle-insights.zip file from the latest release.
3. Extract the ZIP file to a folder on your computer.
4. Open Chrome and go to chrome://extensions.
5. Enable Developer mode using the toggle in the top right corner.
6. Click Load unpacked and select the folder where you extracted the extension.

Option B: Build from Source

If you prefer to build the extension yourself or want to try the latest experimental features:

1. Download or clone the repository from GitHub.
2. Build the extension:

   npm install
   npm run build

3. Open chrome://extensions.
4. Enable Developer mode.
5. Click Load unpacked and select the dist/ directory from the project folder.

3. Configuration & Verification

1. Configure your Profile: Navigate to any YouTube video and click the Subtitle Insights icon in the video control bar. Open Detailed Settings to configure your profile. By default, a Japanese-to-English prompt is provided. Refresh the YouTube page after creating or selecting a profile to apply the changes.
2. AI Ready: Check the extension menu to confirm the AI status. "AI Ready" indicates the models are loaded and functional.
3. Downloading Models: If you see "Downloading Models," Chrome is currently fetching the necessary AI components. This may take several minutes.
4. Enable Captions: Make sure Closed Captions (CC) are enabled in the video player. Subtitle Insights scans these captions to provide the overlay, translations, and insights.