1. What is HTTP?
HTTP (HyperText Transfer Protocol) is a communication protocol used for data exchange between clients (browsers) and servers.
- HTTPS (HTTP Secure): Adds TLS/SSL encryption to secure data transmission.
2. HTTP Request
Structure of an HTTP Request
GET /api/users HTTP/1.1
Host: example.com
User-Agent: Mozilla/5.0
Accept: application/json
| Component |
Description |
| Method |
Defines the request type (GET, POST, PUT, DELETE) |
| URL |
Target resource (e.g., /api/users) |
| HTTP Version |
HTTP/1.1, HTTP/2, HTTP/3 |
| Headers |
Request metadata (Accept: application/json) |
| Body |
Present in POST, PUT requests, contains request data |
Common HTTP Methods
| Method |
Purpose |
GET |
Retrieve a resource (safe, no side effects) |
POST |
Create a new resource (non-idempotent) |
PUT |
Update a resource (idempotent) |
PATCH |
Partially update a resource |
DELETE |
Remove a resource |
3. HTTP Response
Structure of an HTTP Response
HTTP/1.1 200 OK
Content-Type: application/json
Content-Length: 123
{
"id": 1,
"name": "John Doe"
}
| Component |
Description |
| Status Code |
Indicates request success/failure (200 OK, 404 Not Found) |
| Headers |
Response metadata (Content-Type: application/json) |
| Body |
Data returned by the server |
Common HTTP Status Codes
| Category |
Status Code |
Meaning |
| Success (2xx) |
200 OK |
Request successful |
|
201 Created |
Resource created |
| Redirection (3xx) |
301 Moved Permanently |
Permanent redirect |
|
302 Found |
Temporary redirect |
| Client Errors (4xx) |
400 Bad Request |
Invalid request |
|
401 Unauthorized |
Authentication required |
|
403 Forbidden |
Access denied |
|
404 Not Found |
Resource not found |
| Server Errors (5xx) |
500 Internal Server Error |
Server-side issue |
|
503 Service Unavailable |
Server temporarily down |
4. HTTP Headers
| Header |
Purpose |
Example |
Content-Type |
Defines the response format |
application/json |
Authorization |
Authentication token |
Bearer token123 |
Accept |
Specifies accepted response formats |
application/json |
User-Agent |
Client information |
Mozilla/5.0 |
Cache-Control |
Controls caching behavior |
no-cache, max-age=3600 |