T&C LENS
Extension

Introduction

T&C Lens is an open-source browser extension designed to instantly analyze Terms of Service and Privacy Policies. Built with privacy-first architecture, it runs entirely in your browser and ensures your data is never stored.

The internet is built on legal documents that nobody reads. By leveraging advanced Language Models, T&C Lens distills tens of thousands of words into actionable risk scores and precise bullet points in seconds.

Unlike other cloud-based AI tools, T&C Lens operates locally by default. When you use the Bring Your Own Key (BYOK) model, your documents are sent directly to the AI provider of your choice, bypassing our servers entirely.

Installation

T&C Lens is available as a lightweight browser extension. It requires minimal permissions and only activates when you explicitly request an analysis.

Google Chrome

Available soon on the Chrome Web Store.

// Developer Installation

  1. Clone the repository
  2. Run npm run build
  3. Open chrome://extensions
  4. Enable "Developer mode"
  5. Click "Load unpacked" and select the dist/ directory

Mozilla Firefox

Available soon on Firefox Add-ons.

Hosted Tier

For users who want a seamless, plug-and-play experience without managing API keys, T&C Lens offers a Hosted Tier (T&C Lens AI) powered by dedicated infrastructure.

No Artificial Truncation

Unlike the BYOK tier which protects you from massive token bills by truncating long documents, the Hosted Tier securely processes the entire document in one pass. This guarantees absolute precision even on dense, 30,000-word legal texts.

Bring Your Own Key (BYOK)

Developers and power users can use T&C Lens entirely for free by bringing their own API keys. The extension connects directly to your preferred provider's inference API.

Supported Providers

  • Google Gemini

    Recommended for the best balance of speed and cost. Supports Gemini 2.5 Flash and Pro.

  • OpenAI

    High reliability and accuracy. Supports GPT-4o and GPT-4o-mini.

  • DeepSeek

    Incredibly cost-efficient, but API availability may fluctuate based on global demand.

  • Groq

    Near-instant inference speeds using open-source Llama models.

Privacy By Design

T&C Lens operates on a fundamental principle: We do not want your data.

The extension only executes when you click the "Analyze" button. It never runs quietly in the background, it never tracks your browsing history, and it never sends analytics back to a central server.

Architecture Flow

1. User clicks Analyze
2. Extension extracts DOM text from active tab only
3. Extension truncates text (if BYOK is active)
4. Text is transmitted directly from Browser to LLM Provider API
5. JSON response is parsed and rendered in UI
6. Data is purged from memory upon closing popup

Risk Scoring Logic

The AI engine analyzes legal text and extracts clauses based on a strict deterministic prompt. Each identified clause is assigned a severity rating, which contributes to the overall Risk Score out of 10.

High Risk

Clauses that negatively impact user rights, privacy, data, or money (e.g., selling data, forced arbitration, unexpected fees).

Medium Risk

Clauses that have some negative impact but are standard, or important terms users should know about.

Low Risk

Positive, protective clauses (e.g., "we do not sell your data") or harmless boilerplate.

The final score is a weighted average of all extracted clauses. A score of 10/10 represents an extremely hostile document, while a 1/10 represents a highly protective, user-friendly document.

About the Project

T&C Lens is an open-source project built with a strict philosophy: zero dependencies, high performance, and absolute privacy.

  • Tech Stack: Vanilla HTML, CSS, JavaScript. Zero framework dependencies inside the extension.
  • Compatibility: Chrome Manifest V3 and Firefox compatible.
  • Open Source: MIT Licensed. Available on GitHub.

Frequently Asked Questions

Why does the extension say "Document was too long"?

When using the Bring Your Own Key (BYOK) tier, T&C Lens automatically truncates very large legal documents (keeping only the most critical top sections) before sending them to the AI provider. This is a built-in safety mechanism to protect you from accidentally incurring massive token billing costs on your personal API account.

However, if you use the Hosted Tier (T&C Lens AI), the extension completely bypasses this truncation limit and feeds the AI the entire, unshortened document, guaranteeing absolute precision without any surprise bills.

Does T&C Lens store my data?

Absolutely not. T&C Lens operates locally by default. We do not store or keep any of the documents or text you scan. Because no data is collected, there is no document data to delete. If you use the Hosted Tier, you can request complete deletion of your account and billing data at any time.