Is Underbook safe and what data does it collect?

Underbook never sees your payment details or stores identifying information. It only sends the hotel name, your dates, and party size to check prices. No email address or identity is attached to usage statistics, and no IP addresses are stored permanently.

How does Underbook make money?

If you book through a site Underbook surfaces, the company may earn a small commission from that site. You pay nothing extra and the commission never influences which prices are shown.

Can Underbook watch a hotel I already booked?

Yes. Tell Underbook what you paid per night and it checks once a day until your free-cancellation date. It emails you once if a listed rate is at least 5% lower (and at least $5 per night lower) on two daily checks in a row. You must check the room and handle rebooking yourself.

Travel planning

Underbook

Your hotel, double-checked.

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A free browser extension that shows whether another booking site lists the same hotel stay for less and if that cheaper price is for the same room.

About Underbook

Screenshot of the Underbook homepage — Underbook: the homepage

Underbook is a free browser extension for Chrome, Edge, and Firefox that compares hotel prices across booking sites. When you browse hotels on Booking.com, Expedia, Hotels.com, Agoda, or a hotel's own site, Underbook quietly checks other booking sites listed on Google Hotels for the same dates and shows you the results. It displays each price all-in (including taxes and fees where reported), identifies the going rate that most sites agree on, and clearly indicates whether a lower-priced listing names the same room. You always book on the site you choose. Underbook also offers a free web price checker for phones and a price-drop alert feature that emails you if a booked refundable stay drops by at least 5% before free cancellation ends.

What we found

Compares prices across multiple booking sites for the same hotel and dates
Shows all-in prices including taxes and fees
Identifies whether a cheaper listing names the same room
Displays the going rate most booking sites agree on
Price-drop alerts for booked stays
Web price checker for phones and computers without install
Works on Booking.com, Expedia, Hotels.com, Agoda and hotel websites
No account required
Never sees payment information

Pricing

Pricing model: Free

Underbook listing details

Category: Travel planning
Website: underbook.co

Underbook metrics

What we found for underbook.co: Ahrefs Domain Rating and Majestic link details, with changes since the last search.

Domain Rating: 1; +1 (up) since last check
Trust Flow: 0; no change since last check
Citation Flow: 19; no change since last check
Referring domains: 3; no change since last check
External backlinks: 6; no change since last check

Ahrefs Domain Rating found 5 Nov 2026, different since 1 Nov 2026. Majestic found 25 Oct 2026, different since 25 Oct 2026. Link details found by Majestic. Trust Flow, Citation Flow and Topical Trust Flow are trademarks of Majestic-12 Ltd.

0 community votes

Underbook domain, found

See what we found

There is nothing to show, because .co domains have no public RDAP data from their registry.

Find more on underbook.co

Underbook since launch, found

Underbook went live on Business Listing Finder on 25 October 2026. Here is what our readings show since then.
Measure	At launch, then latest
Domain Rating (Ahrefs)	0 to 1 +1 (up) since launch 25 Oct 2026, then 5 Nov 2026
Trust Flow (Majestic)	0 first measured 25 Oct 2026
Referring domains (Majestic)	3 first measured 25 Oct 2026

Day 10 since launch. Next receipt: day 30, 24 Nov 2026. Readings only: they do not prove what caused a change, and many things can. A metric we have no reading for is left out.

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Compare and explore

See the alternatives to Underbook, nextcard vs Underbook, GuideTail vs Underbook, Borderly vs Underbook, Swaphouse vs Underbook, Meridian vs Underbook, Roamify vs Underbook, more in Travel planning.

Common questions

Is Underbook safe and what data does it collect?: Underbook never sees your payment details or stores identifying information. It only sends the hotel name, your dates, and party size to check prices. No email address or identity is attached to usage statistics, and no IP addresses are stored permanently.
How does Underbook make money?: If you book through a site Underbook surfaces, the company may earn a small commission from that site. You pay nothing extra and the commission never influences which prices are shown.
Can Underbook watch a hotel I already booked?: Yes. Tell Underbook what you paid per night and it checks once a day until your free-cancellation date. It emails you once if a listed rate is at least 5% lower (and at least $5 per night lower) on two daily checks in a row. You must check the room and handle rebooking yourself.

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