The Where to Credit API provides mileage earning calculations for frequent flyer programs around the world.

The API accepts a combination of flights and booking classes and, using our rules engine, returns the number of miles earned for each frequent flyer program in JSON format.

Accessing the API

The API can be accessed with these header values from here:

Content-Type: application/json
Accept: application/json

Authorization (Subscribers only)

Subscribers authenticate to API via the Authorization-Token request header value, which must be added to each API request.

Authorization-Token: {{ your-api-key-here }}

Rate Limits (Free users only)

The API is free for personal and small-scale use with no sign-up required. Clients are allowed at most 12 requests per minute and includes a progressive rate limit structure. Rate limits are calculated per request and includes CORS preflight requests.

If your application requires more than the permitted usage limits, consider starting a Subscription Plan or contact us at [email protected] with a description of your application and an estimated usage requirement.

Attribution (Free users only)

Free users must use the following text on every application screen or web page which displays API results: "Data provided by"

Linking from your application and web pages helps us improve the API.


Sample Implementation

Mileage Calculator by

This userscript automatically displays the number of frequent flyer miles you can earn with Expedia, Orbitz, Travelocity, Hotwire, Cheaptickets,, Wotif, and SNCF.

View on GitHub Chrome Extension