Topic
Content Negotiation
See how HTTP clients and servers select representations by media type, language, encoding, and related response metadata.
- HTTP Status Codes
406 Not Acceptable
The server cannot produce a response matching the client's Accept headers. Learn about content negotiation and how to handle format mismatches.
- HTTP Status Codes
506 Variant Also Negotiates
506 Variant Also Negotiates is a server configuration error in transparent content negotiation (RFC 2295). See what triggers it in Apache and how to fix it.
- HTTP Headers
Accept Header
Learn how the Accept header tells servers which content types (JSON, HTML, XML) your client can handle. Master content negotiation and quality values.
- Guides
Content Negotiation: Accept, Languages and Caches
Implement HTTP content negotiation with Accept headers, q-values, Vary and 406 responses, with Express, Django and nginx examples and language SEO guidance.
- HTTP Headers
Content-Location Header
Learn how Content-Location indicates an alternate URL for returned content. Useful for content negotiation and identifying canonical resource locations.
- HTTP Headers
Vary Header: Cache Keys, Vary: Origin and Accept-Encoding
Vary lists the request headers a response depends on, so caches keep separate copies. Vary: Accept-Encoding, Vary: Origin for CORS, Vary: *, and CDN cache keys.
More topics
- 63 pages
Security
Study HTTP security controls for transport, cookies, browser isolation, authentication, content policy, and response hardening.
- 24 pages
Performance
Improve HTTP delivery with caching, compression, connection reuse, timing signals, and response metadata.
- 22 pages
Caching
Learn how browsers and intermediaries store, validate, and reuse HTTP responses with cache directives, validators, and conditional requests.
- 22 pages
Cookies
Understand cookie storage, scope, transport, expiration, and security across HTTP headers, attributes, and session flows.