Definition
A REST API is a web API built on a set of conventions called REST (Representational State Transfer). Data is organised as resources, such as customers, orders or invoices, each with its own web address. Software reads or changes them with standard HTTP methods: GET to fetch, POST to create, PUT or PATCH to update, DELETE to remove. Responses usually come back in JSON, a simple text format. Most public APIs you will encounter are REST APIs.
In a company, a REST API is what your developers or integration partners use to connect systems. Your payment provider, accounting software, CRM and shipping carrier almost certainly offer one. Because REST follows familiar conventions, a developer who has used one REST API can learn another quickly, which keeps integration costs down. REST APIs are also easy to secure, monitor and cache with standard web infrastructure.
REST remains the default for public and internal APIs, coexisting with GraphQL for flexible queries and gRPC for high-performance internal traffic. Good REST APIs come with an OpenAPI specification, a machine-readable description that tools and AI agents can read to generate integrations automatically. The misconception is that REST is a strict standard. It is a style with conventions, so quality varies between vendors, and documentation quality matters as much as the style.
In practice
An e-commerce company integrates a new shipping carrier in 2 days because the carrier offers a well-documented REST API: create a shipment with POST, fetch tracking with GET, cancel with DELETE.
Why it matters
When a vendor says they have an API, it is usually a REST API. Its quality and documentation determine how cheaply your systems connect, which is a real cost in every software decision.
Frequently asked questions
- What does REST stand for?
- REST stands for Representational State Transfer, a term from a 2000 doctoral thesis by Roy Fielding. In practice it means an API where each resource has a web address and is manipulated with standard HTTP methods. Developers use REST as shorthand for this widely shared style.
- What is the difference between a REST API and GraphQL?
- A REST API exposes fixed endpoints, each returning a set structure, so you may need several calls to assemble what you want. GraphQL lets the client specify exactly which fields it needs in one query. REST is simpler and more common; GraphQL suits complex front ends with varied data needs.