What is a REST API? A complete guide for developers

How REST APIs Function in Practice

When you call a REST endpoint, you send an HTTP message across the network. The request communicates to the server what you want to do with a resource, such as create, read, update, or delete.

The response returns what happened as a result. These mechanics consist of three main parts. First, the verbs you send indicate your intent. Second, the status codes you receive confirm the outcome. Third, the headers and bodies transport your actual data.

Understanding these fundamentals transforms REST from abstract theory into practical, debuggable network traffic.

HTTP methods and their purposes

Each HTTP verb maps to a CRUD action:

• GET reads data
• POST creates data
• PUT updates data
• PATCH updates data
• DELETE removes data

This predictable mapping keeps your client code readable and server routes unambiguous.

Idempotency matters for building reliable systems. A method is idempotent when running it multiple times produces the same result as running it once. For example, PUT and DELETE are idempotent, so you can safely retry them. POST is not, meaning duplicate requests usually create duplicate records.

This distinction becomes critical when you build retry logic or add API gateways, because you can safely retry idempotent requests without causing unintended side effects.

Example calls show the pattern in action:

# Read
curl -X GET https://api.example.com/users/42

# Create
curl -X POST https://api.example.com/users \
  -H "Content-Type: application/json" \
  -d '{"name":"Ada Lovelace"}'

# Replace
curl -X PUT https://api.example.com/users/42 \
  -H "Content-Type: application/json" \
  -d '{"name":"Ada Byron"}'

# Partial update
curl -X PATCH https://api.example.com/users/42 \
  -H "Content-Type: application/json" \
  -d '{"nickname":"Countess"}'

# Delete
curl -X DELETE https://api.example.com/users/42

Well-chosen verbs, predictable URLs, and understanding idempotency form the foundation of reliable REST interactions.

Status codes and error handling

HTTP status codes tell you what happened before you parse the response body. Using precise codes enables automated tooling to route, cache, or retry requests correctly. API guidance emphasizes returning accurate codes with structured error bodies.

Here are the most commonly used status codes and their typical applications:

‍

Pair the status code with a JSON body that explains what happened:

{
  "code": 400,
  "message": "email must be a valid address",
  "remediation": "Use RFC-5322–compliant email format"
}

Include a machine-readable error identifier so clients can handle specific errors programmatically. Never expose stack traces or internal details in error responses. Save those for your server logs.

Request and response structure

HTTP headers control how the message gets processed. Content-Type declares your payload format (application/json is standard for most APIs), Accept tells the server what formats you can handle, and Authorization carries your bearer token or API key.

Query parameters handle filtering and pagination without breaking URL conventions:

GET /orders?status=shipped&limit=50&cursor=eyJpZCI6MTAwMH0=

Here, limit sets the page size and cursor gives the server a checkpoint for the next batch—a pattern recommended in design guides for scalable pagination.

A typical JSON response looks like this:

{
  "data": [
    { "id": 1001, "status": "shipped" },
    { "id": 1002, "status": "shipped" }
  ],
  "pagination": {
    "next": "eyJpZCI6MTAwMn0="
  }
}

Use cursors or links instead of raw offsets to avoid missing or duplicating records when data changes between requests. When you support multiple formats—like XML for legacy partners—honor content negotiation so Accept: application/xml returns the same resource in a different format.

Consistent headers, predictable query patterns, and self-describing responses keep your API both human-readable and automation-friendly as your service evolves.

REST API Implementation Best Practices

Building an API that handles real-world traffic requires planning beyond ideal scenarios. Your technical foundation should address four critical areas for successful implementation:

1. Resource design & URL structure

Start by exposing data as nouns, not actions. Endpoints like /users or /orders align with the plural, resource-oriented patterns most developers expect. Verbs belong in HTTP methods, so skip /getUsers or /createOrder.

Hierarchy helps only when it mirrors a clear parent–child relationship. /orders/123/items is readable; four-level paths such as /shops/45/customers/9/orders/123/items grow brittle and complicate caching.

When you need alternatives, like filtering orders by date, prefer query parameters like /orders?status=shipped&date=2024-06-01.

Versioning protects clients from breaking changes. Prefix major versions (/v1/products) or place the version in an Accept header; the URI approach is easier to cache and document. Whatever you choose, apply it consistently so consumers never wonder which format to call.

Finally, keep naming predictable. Stick to lowercase, use hyphens to improve readability (/product-categories), and avoid file extensions.

2. Authentication & security

Traffic must travel over HTTPS, period. Serving plaintext HTTP invites interception. Once encrypted, decide how callers prove identity:

API keys are quick to implement but easy to leak, so you need to restrict scope and rotate frequently. OAuth 2.0 serves as the workhorse for delegated access; pair it with OpenID Connect when you also need identity. JWTs offer self-contained tokens that reduce database lookups.

Rate limiting, input validation, and CORS policies shore up the perimeter. Broken object authorization is one of the most common risks, so check every ID against the caller's privileges before returning data.

A typical authorized request should look like this:

curl -X GET https://api.example.com/v1/orders/123 \
  -H "Authorization: Bearer eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9..." \
  -H "Accept: application/json"

Automate security testing and dependency patching, then monitor failed authentication attempts or bursts of 5XX responses.

3. Documentation & developer experience

Even the cleanest endpoint fails if nobody understands it. Generate an OpenAPI (Swagger) spec directly from code or contract-first definitions. The interactive docs, client SDK generation, and linting that follow are priceless.

Great documentation includes live "Try it" consoles wired to a sandbox environment, copy-paste code samples in cURL, JavaScript, and Python, clear rate-limit headers in every example response, and version and deprecation notices upfront, not buried in change logs.

Error payloads deserve the same rigor. Return a machine-readable structure — code, message, and a docs link — so callers can debug without opening support tickets.

4. Performance & scalability

Performance starts at the wire. Enable gzip or Brotli compression and upgrade front-ends to HTTP/2 to multiplex requests. For read-heavy traffic, expose cache semantics explicitly:

Cache-Control: public, max-age=300
ETag: "a7c3f8d1"

That single header pair lets CDNs and browsers serve repeat GETs without touching your origin, a practice that improves performance significantly.

Data access matters just as much. Index database columns you filter on, and paginate large collections with opaque cursors to avoid OFFSET penalties. For heavyweight workflows — PDF generation or video transcoding — respond 202 Accepted and push the job to a queue, then let clients poll or subscribe to webhooks.

Finally, measure everything. Track P95 latency, error rate, and traffic per endpoint. Sudden spikes trigger autoscaling rules or circuit breakers. Horizontal scale becomes simpler when each node stays stateless—exactly what REST expects.

Implementing REST APIs in Your Projects

When selecting REST APIs for your stack, prioritize integration simplicity, performance reliability, and workflow fit. Good API providers offer clear docs, reliable SDKs, sandbox testing, published metrics, strong uptime guarantees, and support for CI/CD pipelines.

REST works well for most integration needs because it uses familiar HTTP infrastructure with predictable patterns. Building APIs with thoughtful resource design, solid authentication, thorough documentation, and performance tuning creates systems that handle production traffic effectively, scale horizontally, and adapt without breaking clients.

Webflow's CMS offers a RESTful API with these practices built in. Its documented endpoints, consistent patterns, and optimized performance help you build content applications that work smoothly with your existing stack. Try the Webflow CMS API to see how well-designed REST interfaces can accelerate your development process.