Mastering HTTP Headers
Discover how to construct, inspect, and optimize HTTP request/response headers for modern API communication.
1. Header Types
Request Headers
Client-to-server metadata specifying request options: Accept, Authorization, Content-Type
Response Headers
Server-to-client metadata describing response properties: Content-Length, Set-Cookie, Cache-Control
2. Syntax & Usage
Request Example
GET /api/data HTTP/1.1
Host: example.com
Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...
Accept: application/json
User-Agent: MyClient/1.0.0
Response Example
HTTP/1.1 200 OK
Content-Type: application/json
Content-Length: 1234
Cache-Control: public, max-age=3600
{ "items": [ ... ] }
3. Critical Headers
Authorization
Bearer tokens, API keys (required for authentication)
Content-Type
JSON, XML, form-data (specifies payload format)
Cache-Control
max-age, no-cache (directs browser/server caching)
Set-Cookie
Handles session management, authentication cookies
4. Request/Response Lifecycle
Header Exchange
🔁
Request →
Server → ← Response
Headers:
Request →
Server → ← Response
Headers:
Authorization, Content-Type, Set-Cookie
Security Implications
HSTS headers prevent downgrade attacks
CORS headers control cross-origin access
Security headers:
X-Content-Type-Options