APIs are what make a travel website bookable in real time. Airlines, GDSs, bed banks, tour operators and car hire companies provide them so that a booking engine or mid office can search live availability and prices, recheck a price, book, retrieve, amend and cancel without anyone retyping details into a supplier’s website.

How access works

• Formats. Messages are usually written in XML or JSON. XML is older and still common in travel, and IATA’s NDC standard is based on it. JSON is lighter and used by many newer APIs.

• Credentials and testing. Suppliers issue credentials and a test environment, often called a sandbox, and usually certify your connection before giving you live access.

• Limits. Suppliers cap how many requests you can make in a given period, and many also limit the number of searches for each booking, known as the look-to-book ratio.

Example: a customer searches for seven nights in Lanzarote. The website calls a bed bank’s availability API, shows the net rate plus the agent’s mark-up and rechecks the price when the customer chooses a room, if the bed bank requires it. It then makes the booking and stores the bed bank’s reference for any later changes.

Worth knowing

• An API is not a booking engine or a website. It is the connection behind them. A white label gives you a ready-made front end, while with an API you build or choose your own.

• An API does not change anyone’s legal role. If your booking engine combines a flight and a hotel at one price, you are the organiser of a package.

• In travel API documents, OTA often refers to an OpenTravel Alliance message format rather than an online travel agent.