Prices and rooms

From Google Hotels: for your hotel, dates and number of adults, Underbook's price service reads the price each booking site lists there, so a site Google Hotels does not list for that stay is not compared.

It reads Google Hotels' results as data through SerpApi, a search data service. The prices are the public ones a signed-out visitor sees, so a discount you get only when signed in to a site, such as Booking.com's Genius price, is not among them. A result can be up to 30 minutes old, because a priced result is kept that long so a repeat check is fast. If the main lookup fails, a backup provider (MakCorps) is used, and its prices are shown as listed rates in US dollars.

The extension does not read the price on your page: it reads the hotel's name, your dates and the number of adults, and the price of the site you are on comes from Google Hotels' listing for that site. More in How Underbook works.

It means the lower listing names a room whose name matches, under strict rules, a room sold at the going rate; it does not prove the room is the same, and it says nothing about breakfast, cancellation or the other terms of the rate.

The rules: a dorm bed never matches a private room, and the bed type and number, the room category and grade, the view, the bathroom, smoking and accessibility must not conflict; every detail one name states must also be stated on the other. Words about the deal, such as breakfast, refundable, member, prepaid or promo, are left out of the match, so read the rate's terms on the site.

In blind tests on October 1, 2026, a separate AI reader shown only the two room names agreed with 84% of our matches, and with 92% after we tightened the rules, short of the 95% we set as the bar for proof. That is why a matching name is evidence, not proof: check the room on the site before you book (the tests).

Many lower listings name no room at all. From version 0.5.29 the extension, like the web price checker, says which case it is, for example "Super.com doesn't name the room. Check it before you book.", "Different room.", "Similar, but not proof." or "Not clear it is the same room." Older versions say "Different room type possible, check before booking." More: Same room, different price.

All-in is the price per room per night with taxes and fees included, as the booking sites report them to Google Hotels; when no site at that hotel reports a price before taxes, Underbook cannot tell whether taxes and fees are in the numbers, so it calls them a listed rate instead.

A listed-rate result carries the line "Listed rate. Resort/property fees may not be included, verify at checkout." In the first snapshot of our price study that was the case at 31% of hotels. Prices from the backup provider are always listed rates. When a result has no all-in figures at all, it compares prices before taxes and says "All-in totals unavailable for this stay."

All-in is what the sites report. We have not checked prices on checkout pages, so the total on the booking site's checkout page is the one that counts. More: what all-in covers and resort fees explained.

Usually because the two numbers are different kinds of price: Underbook shows the per-night price each site lists on Google Hotels for a signed-out visitor, all-in where the sites report taxes, while the site's own page may show a price before taxes, a total for the whole stay, a member price, or a price that has changed since.

• Taxes: some sites show the price before taxes and add them at checkout, Booking.com shows the total for your whole stay, and Expedia's sites split taxes and fees their own way at some hotels while the total is the same. Compare the totals at checkout.
• Member prices: a price you see only when signed in, such as Booking.com's Genius discount, is not in Underbook's prices, so a site can show you less when you are signed in. It works the other way too: some lower listings ask you to sign in before you can book them.
• Time: a result can be up to 30 minutes old, and offers change or sell out within hours (what we measured).
• Room and terms: the lower price may be for another room or a non-refundable rate (what same room name means).
• Currency and country: every result says which currency its figures are in, and in the extension that is the currency of the booking site you are on, not one taken from your location. In the newest version (from 0.5.33) the banner also says when the prices are the ones listed for a visitor in another country, because a site can show you a different price.
• Party size: prices are per room for the number of adults on the page (2 when the page does not say). For 3 adults or more the banner may show the price per room for 2, and says so.

More: why hotel prices differ across sites.

The going rate is the price most booking sites agree on for that hotel and dates: the most common nightly price (before taxes, where the site reports it) among the listings that name a room or offer free cancellation, or among all listings if none do, with ties going to the lower price.

It is the usual price, not the lowest one. A site counts as lower when its nightly price is more than 5% under the going rate, and price-drop alerts watch the going rate, not the lowest listing. More: what the words on a result mean.