What is REST API?
A REST API is a way for software systems to communicate over HTTP using a set of standard conventions. It exposes resources at predictable URLs and uses methods like GET, POST, PUT and DELETE to read and change data, making integration between applications simple and scalable.
How does a REST API work?
REST stands for Representational State Transfer. A REST API treats everything as a resource - a user, an order, a product - each addressable at a predictable URL such as /users/42. Clients interact with those resources using standard HTTP methods: GET to read, POST to create, PUT or PATCH to update, and DELETE to remove. The server responds with data, usually in JSON, and an HTTP status code that signals success or failure.
A defining trait is that REST is stateless: each request carries everything the server needs to fulfil it, and the server does not remember previous requests. This makes REST APIs easy to scale, because any server in a pool can handle any request without needing shared session memory.
Why REST APIs matter
REST APIs are the connective tissue of modern software. They let a mobile app talk to a backend, let two products integrate, and let third parties build on top of a platform. Because REST uses the same HTTP conventions the web already runs on, almost every language and framework can consume a REST API with minimal effort.
That ubiquity lowers cost and risk. A well-designed REST API can serve a web app, an iOS app and an Android app from one backend, and can be opened to partners later without re-architecting.
What are the principles of a RESTful API?
- Resource-based URLs - nouns that name things, not actions.
- Standard HTTP methods - GET, POST, PUT, PATCH, DELETE used consistently.
- Statelessness - each request is self-contained.
- Meaningful status codes - 200, 201, 404, 500 and others used correctly.
- Consistent structure - predictable request and response formats, usually JSON.
REST API best practices
Use nouns for endpoints and let the HTTP method express the action. Version your API so changes do not break existing clients. Return clear, consistent error messages and the right status codes. Secure every endpoint with authentication and apply rate limiting to protect against abuse. Document the API well, because an undocumented API is effectively unusable by anyone but its author.
How PixelForce approaches REST APIs
At PixelForce, REST API design is part of the architecture work in Phase 1 - Scoping and Design and is built and hardened during Phase 2 - Development, QA and Release. Our in-house team designs APIs to be consistent, versioned and secure from the start, because the API is often the longest-lived part of a product and the hardest to change later. Choosing the right interface style is a deliberate decision we make as part of selecting the mobile app tech stack, weighing REST against alternatives such as GraphQL based on the product, not fashion. For products that depend on robust, scalable backends and integrations, this work sits alongside our enterprise mobile app development capability.
Where this applies
The PixelForce services where REST API matters most - explore how we put it to work in client products.
Related terms
Other glossary definitions closely related to REST API.
Frequently asked questions
REST exposes multiple endpoints, each returning a fixed data shape, so clients sometimes fetch more or less than they need. GraphQL exposes a single endpoint where the client specifies exactly which fields it wants. REST is simpler and benefits from HTTP caching; GraphQL reduces over-fetching and is efficient for complex, nested data. The right choice depends on the product, not on which is newer.
Not exactly. "Web API" is the broad term for any interface accessed over the web, while REST is a specific architectural style for building one. A REST API is a web API that follows REST conventions - resource URLs, standard HTTP methods and statelessness. There are non-REST web APIs too, such as SOAP or GraphQL, so all REST APIs are web APIs but not all web APIs are RESTful.
JSON is by far the most common format for REST APIs because it is lightweight, human-readable and natively supported by JavaScript and most languages. REST itself does not mandate a format - XML and others are possible - but JSON has become the practical standard. Responses typically also include an HTTP status code and headers that describe the result alongside the data.
Always use HTTPS to encrypt traffic, and require authentication on every endpoint, commonly through tokens such as OAuth 2.0 or signed API keys. Apply authorisation checks so users can only access their own data, add rate limiting to deter abuse, and validate all incoming input. Logging and monitoring help detect attacks. Security should be designed in from the start, not added after a breach.
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