Core Methods Overview

GET — Retrieve Data

Purpose:

Fetch data from the server.

Example: GET /api/users/1

Characteristics:

• No side effects (should not modify state)
• Parameters passed via URL

POST — Create Resource

Purpose:

Send data to create something new.

Example: POST /api/users Body { "name": "Alice" }

Characteristics:

• Not idempotent (calling twice creates duplicates)
• Used for form submissions, API creation

PUT — Replace Resource

Purpose:

Replace entire resource.

Example: PUT /api/users/1 Body { "name": "Alice", "age": 30 }

Characteristics:

• Idempotent (same request = same result)
• Full replacement

PATCH — Partial Update

Purpose:

Update part of a resource.

Example: PATCH /api/users/1 Body { "age": 31 }

Characteristics:

• Not necessarily idempotent
• More efficient than PUT

DELETE — Remove Resource

Purpose:

Delete something.

Example: DELETE /api/users/1

Characteristics:

• Idempotent (deleting twice = same result)
• Usually no response body

HEAD — Metadata Only

Purpose:

Same as GET but returns only headers.

Example: HEAD /api/users/1

Use Cases:

• Check if resource exists
• Get content length

OPTIONS — Discover Capabilities

Purpose:

Ask server what methods are allowed.

Example: OPTIONS /api/users

Response: Allow: GET, POST, OPTIONS

Used for:

• CORS preflight requests

Idempotency Explained

Idempotent: Same request → same result

Safe: No side effects

Examples:

• GET /users/1 → always same result
• PUT /users/1 → same data replaces resource
• DELETE /users/1 → deleting again does nothing
• POST /users → creates new each time