De Facto Checker

De Facto Checker is a powerful Chrome Extension that empowers users to verify claims on the web instantly. Powered by an AI-driven backend, it cross-references selected text against reliable sources to provide a groundedness score, detailed reasoning, and citations—all without leaving your current tab.

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🚀 Features

• Context Menu Integration: Simply select text, right-click, and "Verify".
• Non-Intrusive UI: Results appear in the Chrome Side Panel, keeping your workflow uninterrupted.
• AI-Powered Analysis: Uses Perplexity's sonar-pro model for deep semantic verification.
• Source Transparency: Provides clickable citations for every claim.
• Smart Filtering: Automatically excludes the current page from sources to ensure independent validation.

🛠️ Tech Stack

Frontend (Chrome Extension)

• Manifest V3: Secure, modern extension architecture.
• Side Panel API: For a seamless user experience.
• Vanilla JS/HTML/CSS: Lightweight and fast.

Backend (API)

• FastAPI: High-performance Python web framework.
• HTTPX: Async HTTP client for external service calls.
• Pydantic: Robust data validation and settings management.
• Perplexity API: The core intelligence engine.

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📦 Installation

Prerequisites

• Python 3.11+
• uv (Recommended) or pip
• A Perplexity API Key

1. Backend Setup

1. Clone the repository:

   git clone https://github.com/yourusername/de-facto-checker.git
   cd de-facto-checker/src/backend

2. Set up environment variables:

   cp .env.example .env
   # Edit .env and add your PERPLEXITY_API_KEY

3. Install dependencies and run:

   uv run fastapi dev app/main.py

   The server will start at http://localhost:8000.

2. Chrome Extension Setup

1. Open Chrome and navigate to chrome://extensions.
2. Enable Developer mode (toggle in the top right).
3. Click Load unpacked.
4. Select the src/extension directory from this project.
5. The De Facto Checker icon should appear in your toolbar.

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📖 Usage

1. Ensure the backend server is running.
2. Browse any website (news, blog, social media).
3. Select text you want to verify.
4. Right-click and select "Verify with De Facto Checker".
5. The Side Panel will open with the verification result:
   • Grounded Badge: Indicates if the claim is supported.
   • Reasoning: An AI-generated explanation.
   • Sources: Links to external articles confirming (or debunking) the claim.

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📄 License

This project is licensed under the MIT License - see the LICENSE file for details.