🛰️Cache-Control

NEW

An HTTP header that carries directives controlling caching behavior for requests and responses across intermediaries.

DESCRIPTION

Cache-Control is the primary HTTP header for instructing caches and browsers how to store and reuse responses. Directives include max-age, no-cache, no-store, private, public, and s-maxage. Correct configuration improves performance and reduces bandwidth, while misconfiguration can expose sensitive data or serve stale content. Modern HTTP caching is standardized in RFC 9111. Cache-Control supersedes older headers like Expires and Pragma.

ALTERNATIVE DEFINITIONS

MDN Web Docs

The Cache-Control HTTP header field holds directives (instructions) — in both requests and responses — that control caching in browsers and intermediaries.

Clarifies presence in both requests and responses and scope to intermediaries.

Source

IETF RFC 9111

The Cache-Control header field is used to specify caching directives for requests and responses.

Provides the formal standard definition for the header’s role.

Source

RELATED TERMS

Hypertext Transfer Protocol ETag Vary Max-Age S-Maxage RFC 9111 Public Cache Private Cache

COMPETING TERMS

Expires Pragma

RELATIONS

• Conforms to: Hypertext Transfer Protocol

KNOWLEDGE AREAS

Software Engineering Data Integration & Interoperability Data Security

TARGET AUDIENCE

Software Developer DevOps Engineer Security Architect Solution Architect

EXTERNAL SOURCES

• Wikipedia - HTTP#Caching
• MDN Web Docs - Comprehensive Cache-Control reference
• IETF - HTTP caching standard

TOP QUESTIONS

What is the Cache-Control header?

Cache-Control is an HTTP header containing directives that define how responses and requests are cached by browsers and intermediaries.

Category: Definition

How do Cache-Control directives impact performance?

Proper directives reduce repeated network requests and latency. They allow clients to reuse cached content within defined freshness windows.

Category: Relevancy

When should I use s-maxage vs max-age in Cache-Control?

Use s-maxage for shared caches like CDNs, overriding max-age for intermediaries. max-age applies to all caches but is often relevant to browsers.

Category: Requirements

What risks exist with misusing Cache-Control?

Misuse can leak sensitive data via public caches or serve stale content. Always set appropriate privacy and freshness directives.

Category: Risks

What’s the relation between Cache-Control and ETag?

Cache-Control sets caching policy; ETag enables conditional requests to validate freshness, reducing data transfer on updates.

Category: Example

Is Pragma still needed with Cache-Control?

Pragma is legacy. Modern clients rely on Cache-Control and headers defined by RFC 9111 for consistent behavior.

Category: Misunderstanding

How do I prevent caching completely?

Use Cache-Control: no-store and set other headers accordingly. Verify intermediaries honor the directive.

Category: Management

Can Cache-Control be set per request?

Yes. Clients can send Cache-Control directives in requests to influence caching behavior, such as no-cache or max-age=0.

Category: Overview

What’s currently a hot topic with Cache-Control?

Optimizing CDN caching with fine-grained directives and combining Cache-Control with immutable assets is widely discussed.

Category: Topic