REST

REST is the dominant convention for building web APIs. It organises an interface around resources addressed by URL — a customer, an invoice, a list of orders — and uses standard HTTP methods to act on them: GET to read, POST to create, PUT or PATCH to change, DELETE to remove.

Its popularity comes from being unremarkable. It uses the web the way the web already works, so caches, proxies, logs, monitoring and every HTTP client understand it without special handling, and a developer can usually guess what an endpoint does from its URL alone.

The trade-off is that a screen needing data from five resources makes five requests, and each returns everything about that resource whether or not it is needed. That friction is exactly what GraphQL was designed to remove — which does not make REST the wrong choice, because for most systems the simplicity is worth more than the saved round trips.