Cache-Control Inspect

What does this tool do?

Parse Cache-Control and list directives like max-age/no-store/no-cache.

Useful for diagnosing cache hits/misses.

Pair it with HTTP Header Parser by pasting real response headers for faster troubleshooting.

Cache-Control basics (quick)

• Cache-Control defines caching behavior for responses (browser/proxy/CDN, etc.).
• no-store means “do not store”, while no-cache means “must revalidate”.
• max-age is the cache lifetime in seconds.

Typical use cases

• Validate caching for static assets (CSS/JS/images)
• Debug API responses being cached (or not cached) unexpectedly
• Understand CDN vs browser caching (e.g., s-maxage)

Common directives

• public / private: whether shared caches may store it
• max-age: browser cache lifetime (seconds)
• s-maxage: shared cache lifetime (CDN/proxy)
• no-store: do not store (for sensitive responses)
• no-cache: revalidate before use
• must-revalidate: must revalidate once stale

Common pitfalls

• Misunderstanding no-cache as “no caching” (it means revalidate)
• Accidentally making APIs publicly cacheable
• Revalidation not working due to missing ETag/Last-Modified

Recommendations by use case

• API (JSON): use no-store for sensitive data; otherwise no-cache + validators
• HTML: no-cache + must-revalidate or short max-age + validators
• Static assets: long max-age + immutable + versioned URLs

What this tool does

• Split Cache-Control directives
• Inspect values like max-age/s-maxage
• Assist with ETag/Expires/Last-Modified checks

Debugging workflow (recommended)

• Paste response headers
• Review Cache-Control, ETag, and Last-Modified
• Trace 304/206/CDN differences with related inspectors

Operational notes

• Cache behavior changes across browser, CDN, and proxy layers, so compare captures from the same observation point.
• Header-only diagnosis may be insufficient. Also review application cache invalidation strategy and key design.

Referenced specs

• RFC 9111 (HTTP Caching)
• RFC 9110 (HTTP Semantics)
• MDN (Cache-Control / ETag)

FAQ

References

1. RFC 9111 (HTTP Caching)
2. MDN: Cache-Control
3. MDN: ETag

Next to view (diagnostic order)

These links are generated from site_map rules in recommended diagnostic order.

1. How to Diagnose Stale Content After Deployment — Check cache policy by HTML/API/static assets to isolate stale deployment issues quickly
2. How to choose cache tools — Route stale-update, missing-304, and CDN-only mismatch issues to the right tools
3. ETag Inspect — Parse ETag and If-None-Match consistency
4. Cache Control Overview — Summarize how to use Cache-Control/Pragma/Expires together
5. Vary Inspect — Parse Vary and visualize cache variation keys
6. Cache Key Inspect — Visualize cache-key splits from URL, Vary, and headers
7. Cache Not Working Troubleshooting — Troubleshoot cache-not-working symptoms step by step from headers
8. HTTP Cache Mismatch — Identify root causes of cache mismatches

Same-theme links

Cache Control

Diagnose delivery policy across Cache-Control/Expires/Age

• Cache Not Working Troubleshooting — Troubleshoot cache-not-working symptoms step by step from headers
• HTTP Cache Mismatch — Identify root causes of cache mismatches
• Cache Response Analyzer — Judge cacheability from response headers
• Cache Key Inspect — Visualize cache-key splits from URL, Vary, and headers
• Cache Diagnostic — Run cross-header diagnostics for HTTP caching
• Cache Control Overview — Summarize how to use Cache-Control/Pragma/Expires together
• Pragma Cache Inspect — Parse Pragma and inspect legacy cache control behavior
• Expires Inspect — Parse Expires and Date to inspect freshness behavior
• Age Inspect — Parse Age to estimate shared-cache residency time

Example

Cache-Control: max-age=3600, public

Cache-Control: no-store