Early access · Free
Underbook quietly checks if the room you're booking is cheaper somewhere else — and shows you the room and cancellation terms, side by side, so you can decide. You always book where you choose.
Free · no account needed · we never see your payment info.
Underbook isn't in the Chrome store yet.
We're onboarding the first travelers by hand. Already booked a hotel? Tell us the hotel + dates (or paste your confirmation) and we'll double-check the price and email you if it's cheaper — free, no obligation.
We only use this to check your rate. No spam.
A real comparison, run by our engine
Napili Kai Beach Resort · Aug 18–27 · 3 guests · 9 nights
A lower listed rate exists — always verify the room and cancellation terms before booking.
Real output of the Underbook engine. We surface lower rates to verify — we don't claim they're always the same room.
How it works
Browse on Booking, Expedia, Hotels.com, or Google Hotels. Nothing to change.
In the background, Underbook looks for the same stay at lesser-known booking sites — using your own browser.
If it's cheaper, we show the room and cancellation terms side by side. You book on the site you choose.
Most hotel sites hide the fine print. We do the opposite — here's exactly what we will and won't do.
What we promise
What we don't do
Lesser-known booking sites buy hotel rooms through different wholesale channels and spend less on advertising, so their listed rates are sometimes lower. Not always the identical room, though — which is exactly why Underbook shows you the room type and cancellation terms to compare before you book.
We surface the room name and cancellation policy from both sites side by side. When they match, we mark it confirmed. When we can't confirm they're identical, we tell you plainly and show both so you can check — we never assume.
Google does list some of these sites, but they're buried below the sponsored results most people click. Underbook checks them for the exact stay you're looking at and brings the result to you.
If you book through a site we surface, we may earn a small commission from that site. You pay nothing extra. We'll show you the lower rate even when our commission would be smaller — the comparison is for you, not us.
The check runs in your own browser. We never see or store your payment details, and booking happens on the site you choose. We don't sell your data.
We're in early access and onboarding the first travelers by hand. Add it to Chrome above and we'll start double-checking a booking for you, or leave your email and we'll tell you the moment the extension is live.
Free during early access. We'll never see your payment, and you always book where you choose.