Privacy Policy

Last updated: June 4, 2026

Underbook helps you find a lower hotel rate. We collect as little as possible: the extension only does anything on a hotel page, it sends only the hotel name and your dates to our price service, and we never see your payment information. The only personal data we store is the email you give us if you choose to set a price-drop alert.

When the extension is active

The extension can run on the websites you visit, but it only shows anything on a hotel page — a page where it can identify a specific hotel (from the page's title/metadata) and your check-in/check-out dates. On every other page (search engines, email, banking, anything that isn't a hotel) it stays completely idle and shows nothing.

What it reads, and what we send

• On a hotel page, it reads the hotel name and your selected dates from the page.
• It sends only that hotel name and those dates to Underbook's price service (our API at underbook-backend.underbook.workers.dev) to look up and compare current rates across booking sites. We do not send your identity, your browsing history, the other pages you visit, or any payment information.
• We don't use cookies or tracking pixels, and we don't build an advertising profile of you.

Price-drop alerts (optional, opt-in)

If — and only if — you click "Watch this price" and enter your email, we store your email address together with the hotel and dates you asked us to watch. We use this solely to email you if that price drops. We don't use it for marketing and we don't sell or share it. Ask us at hi@underbook.co to stop a watch or delete your email at any time.

What we store on your device

• A local flag recording that you've seen the one-time welcome card.
• If you set a watch, your email is also kept locally (via chrome.storage.local) so you don't have to retype it. It stays on your device.

How Underbook makes money

When you open a booking site through Underbook and complete a booking, we may earn an affiliate commission from that site — at no extra cost to you (you pay the same price you'd pay going there directly). This never changes which rates we show you or the order we show them: we always surface the genuinely lowest rate we find, and we'll link you to a cheaper option even when it earns us nothing. We never take payment from you, and we don't sell your data.

What we never do

• We never see, store, or transmit your payment details — you always book directly on the site you choose.
• We don't sell or share your data.
• We don't track you across the web or record your browsing.

Permissions, and why

• Access to the sites you visit: so the comparison can appear on any hotel page — major booking sites and individual hotels' own websites. The UI only activates when a hotel + dates are detected; nothing happens on other pages.
• activeTab & scripting: so that when you click the Underbook icon, it can check the hotel page you're on.
• Storage: to remember the welcome card and, if you set a watch, your email.
• Connection to our price service (underbook-backend.underbook.workers.dev): where the rate comparison is performed.

The website (separate from the extension)

If you join the waitlist on underbook.co, you give us your email, which we use only to contact you about Underbook. We don't sell it.

Contact

Questions, or want your data deleted? hi@underbook.co.

We'll post any material change to this policy on this page with a new "last updated" date.