Cache Response Analyzer

Analyze cache-related headers across layers. No input is sent to a server. Use it for first-pass revalidation and CDN mismatch troubleshooting.

Status

Runs in your browser. No input is sent to a server. Use this as a first-pass diagnostic step.

How to use

Paste response headers and click “Analyze”. It shows cacheability/shared-cache eligibility/revalidation.

Notes (this tool)

  • This analysis is header-centric. Verify app logic and CDN overrides separately.
  • Effective cache keys change with Vary, so the same URL can produce different cache behavior.

About this page

What does this tool do?

Judges cacheability from Cache-Control / Expires / Age / ETag / Last-Modified, etc.

Debugging workflow (recommended)

  • Paste response headers and get a verdict
  • Use Cache Diagnostic for deeper analysis
  • Use individual Inspect tools to pinpoint causes

Recommendations by use case

  • API (JSON): no-store or no-cache + validators
  • HTML: short max-age + validators / no-cache
  • Static assets: long max-age + immutable + versioned URL
  • Cache Diagnostic
  • Cache-Control Inspect
  • Expires Inspect
  • ETag Inspect
  • Last-Modified Inspect

What this tool does

  • Judge cacheability/shared-cache eligibility/revalidation
  • Show freshness and its basis

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)

FAQ

Can this tool alone identify the root cause?

It is effective for first-pass judgment, but path-specific issues require follow-up tools.

When should immutable be used?

Use it mainly for versioned static assets. It is usually not suitable for HTML.

References

  1. RFC 9111
  2. RFC 9110

Page-specific case studies

This tool evaluates cacheability from a single response and is useful for first-pass validation.

  • Determine private/public and no-store/no-cache semantics first.
  • Check the combination of max-age, s-maxage, and immutable.
  • If Expires is present, verify it is consistent with Cache-Control.

Page-specific implementation checklist

  • Fetch the same URL with both curl and browser devtools.
  • Express shared-cache policy explicitly with s-maxage.
  • Introduce immutable only with a clear update strategy.
  • Include analyzer checks in pre-release validation.

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

  1. Cache Not Working Troubleshooting — Troubleshoot cache-not-working symptoms step by step from headers
  2. HTTP Cache Mismatch — Identify root causes of cache mismatches
  3. Cache Diagnostic — Run cross-header diagnostics for HTTP caching
  4. How to Diagnose Missing 304 Responses — Trace ETag/Last-Modified and If-* round trips to isolate missing 304 behavior
  5. How to Diagnose Stale Content After Deployment — Check cache policy by HTML/API/static assets to isolate stale deployment issues quickly
  6. How to choose cache tools — Route stale-update, missing-304, and CDN-only mismatch issues to the right tools
  7. Cache Key Inspect — Visualize cache-key splits from URL, Vary, and headers
  8. Cache Control Overview — Summarize how to use Cache-Control/Pragma/Expires together

Cache Control

Diagnose delivery policy across Cache-Control/Expires/Age