Privacy Policy

Last updated: May 21, 2026

Short version: We don't sell your data, we don't store your lookups, and you don't need an account to use the free tier. Selected text is sent to our server only to generate your explanation and is not retained.

1. What data we collect

When you use the Professor Chrome extension to look up a word or phrase, the following data is sent to our server (professor-api.professorai.workers.dev):

The selected text — the word or phrase you highlighted
Surrounding context — up to ~150 characters around your selection, to improve explanation accuracy
Domain hint — the detected subject area (finance, legal, medical, etc.) derived from the page's URL and content keywords
A device ID — a randomly generated UUID stored locally in your browser, used only to enforce the free daily lookup limit. It contains no personal information and is not linked to your identity.

We do not collect or store the URL of the page you are reading, your browsing history, your name, email address, or any other personally identifiable information during free-tier use.

2. How we use the data

The selected text and context are sent to Anthropic's Claude API to generate your explanation. The response is returned to your browser and displayed in the extension popup. We do not store the text of your lookups on our servers.

The device ID is used only to count daily free lookups (limit: 10 per day). The count resets after 48 hours and is stored in Cloudflare KV with automatic expiry. The device ID itself is not linked to any personal identifier.

3. Pro account data (when you sign in)

If you create a Pro account, we collect:

Your email address (via Clerk, our authentication provider)
Your subscription status and plan (via Stripe, our payment processor)
Your lookup history, if the "Save lookups" setting is enabled (on by default for Pro users, opt-out available in Settings)

Stripe processes all payment information directly. ProfessorAi never sees or stores your credit card number.

4. Blocked domains

Professor is disabled by default on banking, financial account, password manager, and HR portal websites. You can view and edit this blocklist in the extension Settings panel. When a domain is blocked, Professor does not activate on that page — no text is captured or transmitted.

5. Data sharing

We share your data with the following third parties only as necessary to operate the service:

Anthropic — receives the selected text and context to generate explanations. Subject to Anthropic's Privacy Policy.
Cloudflare — hosts our Worker API and KV storage. Subject to Cloudflare's Privacy Policy.
Clerk (Pro accounts) — manages authentication. Subject to Clerk's Privacy Policy.
Stripe (Pro accounts) — processes payments. Subject to Stripe's Privacy Policy.

We do not sell, rent, or share your data with advertisers or data brokers.

6. Cookies and local storage

The extension stores the following data locally in your browser using chrome.storage.local and chrome.storage.sync:

Your device ID (random UUID)
Your daily usage count and reset date
Your extension settings (theme, explanation length, blocklist, trigger mode)
The last saved popup position on screen

This data never leaves your browser except as described in Section 1. You can clear it at any time via Settings → Clear local data.

7. Children's privacy

Professor is not directed to children under 13. We do not knowingly collect data from children under 13.

8. Changes to this policy

We may update this policy as the product evolves. We will update the "Last updated" date above. Continued use of the extension after changes constitutes acceptance of the updated policy.

9. Contact

Questions about this privacy policy? Email us at privacy@professorai.com.