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Repair Windows errors before they cause bigger problemsFix Now →Scan for outdated or missing drivers - takes under a minuteDriver Scan →A RESTful API is an interface designed according to Representational State Transfer (REST), an architectural style for distributed systems. It exposes identifiable resources, exchanges representations of those resources, and uses a uniform, self-descriptive interface—usually HTTP. JSON is commonly used, but JSON is only a representation format and does not make an API RESTful by itself.
In everyday developer speech, “REST API” often means an HTTP API with URL endpoints and methods such as GET and POST. That shorthand is useful, but an API is formally RESTful only when it follows REST’s broader constraints, especially stateless requests, a uniform interface, cacheability, layered operation, and (in the complete model) hypermedia controls.
RESTful API in one example
Imagine an API for users. The conceptual resource is a user, and /users/42 identifies one user. A client might send:
GET /users/42 HTTP/1.1
Host: api.example.com
Accept: application/jsonThe server returns a representation of the user, perhaps JSON:
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{
"id": 42,
"name": "Amina Lee",
"email": "amina@example.com"
}The URI identifies the resource; the HTTP method expresses the requested operation; headers describe the request and desired representation; and the response carries the current state in a transferable format. A different representation, such as HTML or XML, could describe the same resource without changing the resource itself.
A route and a set of HTTP verbs do not prove that an API satisfies every REST constraint. They show a resource-oriented HTTP design, which is often what developers mean by “REST API.”
What do API, resource, representation, and REST mean?
API
An application programming interface is a contract through which software requests data or actions from another component. The contract defines addresses, inputs, outputs, errors, authentication, and interaction rules.
Resource
A resource is the conceptual thing being addressed: a user, invoice, image, collection, document, or weather service. It is not necessarily one database row or one file. In Roy Fielding’s formulation, a resource is a stable conceptual mapping whose values or representations can change over time.
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A URI identifies a resource. For example, /orders/781 names an order, while /orders commonly identifies an order collection. The identifier should remain meaningful even as the order’s data changes.
Representation
A representation is the transferable description of a resource’s current or intended state, including data and metadata. JSON, HTML, XML, and images are representation formats. A response may include a media type such as application/json in its Content-Type header.
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REST
REST stands for Representational State Transfer. It is an architectural style, not a protocol, programming language, framework, or mandatory data format. HTTP is its familiar web implementation, but REST is conceptually broader than HTTP.
REST constraints that define the architectural style
1. Client-server separation
The client handles user-interface concerns, while the server handles data storage and business rules. Because the responsibilities are separated, each side can evolve independently as long as the interface remains understandable.
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2. Stateless interaction
Every request must contain the information the server needs to understand it. The server does not depend on conversational context retained from a previous request. A client therefore sends credentials, resource identifiers, parameters, and other required context on each request, often through an authorization header.
Stateless does not mean that an application has no state. Databases, orders, sessions represented by tokens, and client-side workflows can all have state. The constraint means that request interpretation does not rely on hidden server-side conversation history.
3. Cacheability
Responses must indicate whether they may be reused. HTTP cache directives such as Cache-Control, validators such as ETag, and expiration rules let clients and intermediaries avoid repeating identical work. Caching can reduce latency and server load, but stale or private data must not be reused incorrectly.
4. Uniform interface
Fielding called the uniform interface REST’s distinguishing feature. It gives clients a general way to interact with resources instead of a separate custom protocol for every operation. It has four related constraints:
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- Identification of resources: resources have stable identifiers.
- Manipulation through representations: clients submit representations to create or change resource state.
- Self-descriptive messages: methods, status codes, headers, and media types explain how to process a message.
- Hypermedia as the engine of application state (HATEOAS): representations provide links or controls that indicate available next actions.
Fielding summarized the central idea as: “The central feature that distinguishes the REST architectural style from other network-based styles is its emphasis on a uniform interface between components.”
5. Layered system
A client may communicate through proxies, gateways, load balancers, caches, or API gateways without needing to know whether it is connected directly to the origin server. Each layer performs its permitted role while preserving the interface.
6. Code-on-demand (optional)
A server may extend a client’s capabilities by transferring executable code, such as a script. This is the one optional REST constraint; an API can be RESTful without using it.
HTTP methods and their intended semantics
HTTP defines method semantics independently of REST. A resource-oriented API uses those semantics consistently rather than inventing a different meaning for each endpoint.
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|---|---|---|---|
GET |
Transfer a current representation of the target resource | Safe and idempotent | Read a user or list orders |
POST |
Submit content for resource-specific processing | Not generally idempotent | Create an order or trigger processing |
PUT |
Replace the target resource’s current representation | Idempotent | Replace all editable fields of a profile |
DELETE |
Remove the target resource’s current representations | Idempotent | Delete a saved address |
PATCH |
Apply a partial modification | Depends on the patch operation | Change only an email field |
Safe means the client does not request a state change. A safe request can still cause incidental effects such as logging or billing for infrastructure. Idempotent means that repeating an identical request has the same intended effect as making it once; individual responses and incidental logging can still differ. In RFC 9110, GET, HEAD, OPTIONS, and TRACE are safe, while safe methods plus PUT and DELETE are idempotent. The core HTTP method table does not define PATCH semantics; the selected patch format and operation determine its behavior.
How a resource-oriented API is organized
Collections and individual resources
Use nouns for resource identifiers: /users, /users/42, and /users/42/orders. The method supplies the action. GET /users lists users; GET /users/42 retrieves one; POST /users submits a new-user representation; and DELETE /users/42 requests removal.
Representations and content negotiation
A client can indicate what it accepts with Accept, while the server identifies the returned format with Content-Type. The same conceptual resource might be represented as JSON for an application and HTML for a browser. Avoid treating a database schema as the API’s public representation: the API contract should expose stable concepts and deliberately chosen fields.
Status codes and self-descriptive messages
Use status codes to communicate the broad result: a successful retrieval, a created resource, a client error, or a server failure. Include enough headers and body information for a client to process the result without undocumented knowledge. Error responses should state which input failed and, where practical, how to correct it.
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Hypermedia controls
In a fully RESTful design, a response can include links or forms for valid next actions. For example, an order representation might link to payment, cancellation, and shipment tracking only when those actions are currently available. This lets clients discover transitions instead of hard-coding every workflow URL.
REST API versus API: what is the difference?
“API” is the broad category: a library API, operating-system API, database API, RPC interface, GraphQL service, and HTTP service are all APIs. “REST API” is a narrower label for an API intended to use REST’s resource-oriented constraints, usually over HTTP.
Many services called REST APIs use HTTP endpoints and JSON but omit hypermedia, rely on server-side conversational state, or assign custom action meanings to URLs. MDN therefore uses “REST API” as common terminology while cautioning that such APIs do not necessarily satisfy every REST constraint. When the evidence only establishes HTTP endpoints and verbs, “HTTP API” is the more precise description.
REST compared with operation-oriented designs
A resource-oriented interface favors a small, consistent vocabulary: identify a resource, exchange representations, and use standardized method semantics. An operation-oriented RPC interface instead exposes procedures such as createInvoice or approvePayment. Neither approach is universally faster or better.
| Concern | REST approach | Operation-oriented approach |
|---|---|---|
| Primary model | Resources and representations | Named procedures or commands |
| Interaction vocabulary | Uniform methods, status codes, headers, and links | Application-specific operations and arguments |
| Discovery | Can use hypermedia controls | Usually follows a separately documented operation list |
| Caching | Benefits from standard HTTP cache semantics | Requires operation-specific decisions |
| Trade-off | Generality and independent evolution | Potentially more direct expression of specialized actions |
How to evaluate whether an API is genuinely RESTful
- Can each important conceptual resource be identified independently?
- Does the API manipulate resources through representations rather than exposing only database commands?
- Are HTTP methods, status codes, headers, and media types used according to their standard meanings?
- Does every request include the context needed to understand it?
- Do responses clearly state caching rules?
- Can proxies, gateways, and caches operate as layers without changing the client contract?
- Do representations expose links or controls for available state transitions, where full REST compliance is claimed?
If the answer to the last question is no, describe the service accurately as an HTTP API or resource-oriented HTTP API rather than claiming complete REST compliance.
Benefits and trade-offs
- Interoperability: standard HTTP semantics work with browsers, proxies, caches, command-line tools, and many languages.
- Visibility: stateless, self-descriptive requests are easier for intermediaries and operators to inspect.
- Independent evolution: client and server can change separately when the interface remains stable.
- Cache efficiency: cacheable responses can avoid repeated network work.
- Generality cost: a uniform interface may be less optimized than a narrowly tailored protocol.
- Repeated context: stateless requests can repeat authentication and other information, increasing message size.
- Workflow complexity: hypermedia and versioned representations require deliberate client design.
Or skip the browser setup: ScreenshotNeo as an HTTP API example
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cURL:
curl -G "https://api.screenshotneo.com/v1/shot" -d access_key=YOUR_API_KEY --data-urlencode url=https://stripe.com -o shot.webpPython:
import requests
r = requests.get("https://api.screenshotneo.com/v1/shot", params={"access_key": "YOUR_API_KEY", "url": "https://stripe.com"}, timeout=90)
open("shot.webp", "wb").write(r.content)Node.js:
const q = new URLSearchParams({ access_key: 'YOUR_API_KEY', url: 'https://stripe.com' });
const res = await fetch(`https://api.screenshotneo.com/v1/shot?${q}`);See the ScreenshotNeo documentation for request options. Its MCP server supplies take_screenshot, get_page_info, and capture_pdf tools to Claude, Cursor, and other MCP clients. Every plan includes its features; 1,000 screenshots per month are free with no card, and paid plans start at $5 for 3,000 screenshots. Sign up free.
Frequently Asked Questions
Does REST require JSON?
No. REST can transfer JSON, HTML, XML, images, or another media type. JSON is a representation format, not a REST constraint.
Is REST the same as HTTP?
No. HTTP is a protocol commonly used to deploy REST-style interfaces; REST is an architectural style with broader constraints.
Is POST always for creating resources?
No. HTTP defines POST as resource-specific processing. Creation is common, but a POST request can also submit data for another server-defined process.
What does stateless mean when users log in?
Each request still carries the context needed for authentication, such as a token. The application may retain user and business state; the server simply does not require hidden conversational context from an earlier request.
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