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How we work

Introduction

A simple search on KAYAK scans for prices on hundreds of travel sites in seconds. Whether you’re looking for flights, hotels, rental cars, or more, we gather deals from across the web and put them in one place. Compare your options for the same flight, hotel or rental car and choose where you book—whether it’s directly with the airline, hotel or car agency—or even from another travel site.

Prices come straight from the travel sites to your screen, with no extra fee from KAYAK. When you’ve chosen your preferred deal, the provider of that deal simply pays us for either redirecting you to their site or helping you to book with them. This makes our service totally free for our users.

Another way we earn money is by displaying travel-related advertisements on our site. Some companies even pay us when you click on an advert that interests you.

We are not a travel agent, do not sell flight tickets or make reservations, and are not involved in the payment. Upon selecting a travel option to reserve, you leave our website; please check the details and conditions on the travel site before completing the reservation.

Table of contents

How we recommend content and list results.

Our recommender systems

We use recommender systems on our sites to help you discover content we think you will like, by weighting factors such as where we believe you are (based on country site, currency selected, IP address or the home airport you have set), what you tell us in the search form (origin, destination, dates, number of guests, etc.), the price of offers and the popularity of destinations or offers, and sometimes our expected revenue. Each factor can be more (or less) important in different cases, depending on what we think is most likely to produce content that is relevant for you.

For example on our landing pages, you will find a number of recommender systems, including:

“Compare vs [our brand]”: Other sites you can use to search for travel, recommended based on travel origin/destination and expected revenue for us.

“Explore the World from”: Destinations you may want to travel to from your current location, based on your home or origin airport, search dates, prices for flights to and popularity of the destinations.

“Hop on, hop off”: Destinations you can reach with a direct flight, based on your home or origin airport, non-stop routes available from there in the next month and popularity of these destinations.

“Stays near you”: Cheap accommodation in your area or your destination.

“Explore a variety of stays“: Accommodation in your area or your destination grouped by property types.

“Favourite hotels around the globe”: Hotels you may want to visit, in a rotation pulled from a manually curated list.

“Drive around in”: Cheap rental cars grouped by car categories based on your search destination and dates.

“Your wishlist starts here”: Destinations you may want to save to your wishlist, based on your home or origin airport and the popularity of destinations from there

“Explore” allows you to search for flight destinations by budget and duration, by default based on cheap offers found by other users and ranked by price.

“KAYAK Assistant” allows you to use an AI prompt to ask for flights that match certain criteria, and it will match the free form text you have entered to available filters and apply these filters.

“Recommended Filters” will recommend you personalised filters based on your past user behaviour and/or the context of the locations being searched, as well as your search parameters (e.g. dates, number of passengers, cabin class); this could also include popular filters for a given location based on usage on our sites as we believe that users may want to reuse certain filters based on their preferences across multiple searches within a vertical.

Our travel search results are also a recommender system, so please check out the ranking options below for each category:

Flights

Best and Recommended

Just because a deal is cheap doesn’t mean it’s necessarily the best. So by default flights are ranked to give you the best trade-off between price and convenience, based on factors such as duration, price, distance between origin and destination, number of travellers and how you started your search, while applying a result diversity logic to provide you with an array of airlines and time-of-day options. The relative importance of the factors is specific to each set of search results, e.g. price will be less relevant if the cheapest flight is only slightly cheaper, but a lot longer than the quickest flight. We believe that these parameters and their weighting contribute to displaying more relevant search results to the users, since the savings on the cheapest flight option may not justify the hassles such as a long stopover that come with it.

Sometimes, the same flight will be available on several provider sites. We highlight the cheapest provider, and the order of the other booking options will be based mainly on click-through-rate and cost per click. In case of price parity between several booking options for the same flight, the order of booking options will be based mainly on click-through-rate and cost per click. We sometimes also judge the quality of the service you’re getting from a provider site. We’ll highlight things like a provider’s booking or baggage fees, so that when you compare your options, you’re using the total price. And if a provider isn’t upfront with their fees, making their prices less clear, we’ll tend not to recommend them.

We display deals from many different sources, including airlines, aggregators, global distribution systems, travel management companies, online travel agencies; however, our results may not always reflect all available deals.

Cheapest

Looking for the lowest price? We can make that happen. Our price sort gives you quick access to the cheapest and/or the most expensive deals—it’s your trip, so it’s up to you.

Sometimes, the same deal will be available on several provider sites. All of these providers are made visible for you to choose from, but we highlight one main provider based on factors like customer popularity or ratings. Providers can also become highlighted if they pay more for the clicks they get.

Stays (hotels and other accommodations)

We use internal algorithms to rank property results as well as sort booking option providers within a given property result. For visual simplicity, we always round up the price to the next whole number.

For property results ranking: by default, results are ranked by our ‘Recommended’ algorithm, which is based on a few key parameters: price, guest ratings and its popularity (measured in clicks). The relative importance of the parameters is specific to each set of search results, e.g. price will be less relevant if the price difference is very small. We also factor in the average revenue potential for us from each hotel result. We believe that these parameters prioritise the most relevant results for the users, while also improving our revenue. We use additional parameters such as the distance from city-centre and the number of stars, which we deem less relevant and therefore attribute a lower weighting. You can also sort the results by price, hotel class, review score, and distance (from the destination in your search).

Sometimes, the same deal will be available on several provider sites. We highlight one main provider based on factors such as provider’s price compared to the solo cheapest price and the average revenue potential for us from each hotel result, i.e. an offer may be ranked higher if our expected remuneration is higher, but not if it is substantially more expensive than the other offers. Our algorithms may obfuscate one or several offers if they are not the solo cheapest and they are affecting our or our partner’s monetisation. We believe that these parameters balance the relevance of results for the users and improving our revenue. Within a hotel listing, if the solo cheapest offer is not displayed above the “View Deal” or “Select” button, you can see it by looking for the price highlighted in green. The ordering favous private deals if the user is logged in.

Price

Looking for the lowest price? We can make that happen. Our price sort gives you quick access to the cheapest and/or the most expensive deals—it’s your trip, so it’s up to you.

Cars

The “recommended” sort for car rental is mainly prioritised by price, revenue potential for us, general click popularity and the popularity of different car classes in each pick-up destination (e.g. SUVs are more popular than normal at this pick-up location). For some locales, we also factor in the review score of each rental agency and/or deal providers. The relative importance of the factor is specific to each set of search results.

Sometimes, the same deal will be available on several provider sites. We highlight one main provider based on factors like customer popularity or ratings. Providers can also become highlighted if they pay more for the clicks they get. Our algorithms may obfuscate one or several offers if they are not the cheapest and they are affecting our or our partner’s monetisation. We believe that these parameters balance the relevance of results for the users and improving our revenue. Within a car listing, if the cheapest offer is not displayed above the “View Deal” or “Select” button, you can see it by looking for the price highlighted in green.

Flight+Hotel/Holidays

The default “Recommended” sort result for holidays is based mainly on the price, the hotel’s guest rating and its popularity (measured in clicks). We also factor in the average revenue potential for us from each holiday result. We believe that these parameters prioritise the most relevant results for the users, while also improving our revenue.

Within a flight+hotel listing, we order our results based on an internal algorithm that balances the prices and our revenue potential for the results shown.

Trains and Buses

Departure time

We have sorted our train and bus results by departure time to make it easier to find an itinerary that matches your schedule.

Cheapest

Looking for the lowest price? We can make that happen. Our price sort gives you quick access to the cheapest and/or the most expensive deals—it’s your trip, so it’s up to you.

Our train and bus prices sometimes include mandatory taxes and fees, depending on locale. Check for additional fees. Some partners may charge for an additional service fee, a fee for additional baggage, or a fee for certain payment methods.

How we get prices.

We search hundreds of travel, airline, hotel and rental car sites at once to bring you options from across the web. While we always strive to have the most accurate and current information, there are occasional inaccuracies. Sometimes, it’s because the provider site isn’t updating their inventory with us or hasn’t connected to our site properly, or maybe another traveller has already booked that deal. This last scenario will sometimes happen because we cache results in order to keep site speed up (so you’re not waiting around). For example, if you and another traveller start the same search within the same minute then we’ll most likely show you both the same results. At the very least, provider sites should give us an updated inventory of prices every 24 hours. While we do search as many sites as we can, we’re still not able to search them all. There are also cases where we don’t display results from certain providers for technical or commercial reasons, or simply because we can see them having a negative effect on customer satisfaction.

How we get reviews and moderate content.

Reviews appear on our site in a few ways. We show reviews and review scores from other well-known travel websites.

On our site, we collect and display reviews in a few different ways.

For Flights and Cars, we display reviews collected directly from our customers who have a confirmed booking, whereas for Stays, we display reviews from both our customers and from partner websites. For reviews collected directly from our customers, only users who have an account with us and agree to receive emails from us are contacted and asked to provide a review. Customers may also leave reviews directly on our Trips platform.

The customer will only be contacted after the reservation has concluded, which ensures that our reviews contain first-hand knowledge and reflect customers’ personal experiences. For Flights and Cars, the user selects a rating from “poor” to “excellent.” We then convert this into a numerical rating on a scale of 1 to 10 and attach it to a qualitative review (if provided) to facilitate easy comparison and evaluation. Our method eliminates fake reviews or social media endorsements, and instead relies on verified customers to provide genuine reviews. For reviews on Stays, our scores are calculated by averaging the scores of reviews that we collect and reviews collected by our partners.

All reviews are published after doing automated profanity checks. Whether positive or negative, we won’t display or will remove reviews that violate our guidelines or terms of review providers, similar to our Terms of Use, including reviews that include or refer to (among other things):

  • Illegal activities;
  • Personal or sensitive information;
  • Swear words, sexual references, hate speech, discriminatory remarks, threats, etc.
  • Impersonation;
  • Comments unrelated to the topic or intended use of our website, including comments relating to the booking experience instead of the relevant travel experience
  • Spam and fake content.

And to make sure reviews are still relevant, we may stop showing reviews once they are three years old – or if there has been a change of ownership or another major change such as a renovation.

We may also ask users to submit travel tips. These tips are evaluated through automated means and will not be published if they are not deemed sufficiently useful.

We will also remove illegal content and reviews that do not comply with the above after manual review by our content moderation team based on a notice sent to us through the feedback form.

If our decision to remove content can be appealed pursuant to article 20 of Regulation (EU) 2022/2065, we will provide a statement of reasons for our decision and information on how to lodge a complaint against the decision. Any complaints will be reviewed manually by our content moderation team against our content guidelines and the outcome of the review will be notified to the complainant.

If a recipient of the service is frequently found to provide manifestly illegal content or someone is frequently submitting notices or complaints that are manifestly unfounded as envisaged in article 23 DSA, then we will review the matter in accordance with article 23(3) DSA and, if the repeat offence is confirmed, we will issue a warning to the person in question, respectively suspend them after a prior warning. At this time we do not envisage such cases happening and will give examples of the facts and circumstances that we take into account when assessing whether certain behaviour constitutes misuse and the duration of the suspension if and once we see such cases.

How we work with other companies.

We have contractual partnerships with most of the 700+ provider sites that can be seen in our results. If you’re a company that’s interested in working with us, check out our Partners contact page.

Our company forms part of Booking Holdings Inc., which includes other travel and leisure sites such as Booking.com, Priceline.com, Agoda.com, Rentalcars.com and Opentable.com.

We also operate a portfolio of metasearch brands, including KAYAK, SWOODOO, checkfelix, momondo, Cheapflights, HotelsCombined and Mundi.