# What is REST API?

Also called RESTful API, representational state transfer.

A REST API is a web interface organized around resources identified by URLs, manipulated with standard HTTP methods, and exchanged in a common format such as JSON. REST, short for representational state transfer, is an architectural style described in 2000 rather than a protocol, and most interfaces called REST follow only part of it.

The conventional mapping uses GET to read, POST to create, PUT or PATCH to update, and DELETE to remove, addressed at paths such as /invoices and /invoices/42. Status codes carry the outcome, so a caller can distinguish a missing record from a rejected input from a server fault without parsing prose. Servers are expected to be stateless, holding no per client session between requests.

Predictability is the real value. Because so many services follow the same conventions, a developer or an agent can guess the shape of an unfamiliar interface and be right most of the time. That regularity is also what makes automatic client generation, caching, and generic tooling possible across services that were never designed together.

Strictly, the style requires more than most implementations provide, including responses that carry links describing what a client may do next. Almost no commercial service does this, so what ships is usually better described as an HTTP JSON API. The looser usage is now so widespread that arguing about it rarely helps, but it is worth knowing the label is imprecise.

Neighboring styles trade differently. A query language style lets a client request exactly the fields it needs in a single round trip, and binary remote procedure call frameworks trade human readability for speed. For agents, plain HTTP interfaces have a quiet advantage, since predictable endpoint names and clear error messages are also easier for a model to use correctly.

## Key points

- Resources at URLs, manipulated with standard HTTP methods.
- Status codes carry outcomes and servers hold no client session.
- REST is an architectural style from 2000, not a protocol.
- Most so called REST APIs are really HTTP JSON APIs.
- Predictable conventions help both developers and agents.

## In practice

A task manager exposes /tasks. A GET to /tasks returns a list, a POST with a JSON body creates one and replies with a 201 status and the new task's URL, a GET to /tasks/17 returns that single task, and a DELETE to the same path removes it. A developer who has never opened the documentation can predict most of this, which is precisely the point of the convention.

## Related terms

- [API](/en/glossary/api)
- [Webhook](/en/glossary/webhook)
- [SDK](/en/glossary/sdk)
- [Rate Limiting](/en/glossary/rate-limiting)
- [Idempotency](/en/glossary/idempotency)

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