Cache Key Inspect
When the same URL behaves differently in cache, this tool visualizes which headers or query parameters split the cache key.
Status
Runs in your browser. No input is sent to a server. Useful for first-pass cache-key split analysis.
How to use
Paste URL and headers, then click “Analyze”. It summarizes base key, Vary dimensions, and operational warnings.
Notes (this tool)
- Actual CDN key normalization depends on vendor configuration.
About this page
What does this tool do?
Given request URL and request/response headers, it estimates base key (method+URL) and additional dimensions from Vary.
It also warns about query/header patterns that commonly cause key explosion.
Typical use cases
- Investigate why CDN hit ratio is unexpectedly low
- Validate whether Vary is missing or over-specified
- Check whether query parameters are inflating key cardinality
How to read key composition
- Base key: method + scheme + host + path + query
- Additional dimensions: request headers listed in Vary
- Even same URL can split into separate objects by Vary dimensions
What this tool does
- Visualize candidate cache key (base + Vary)
- Warn on Vary:* and excessive key cardinality
- Check consistency between Vary and Content-Encoding/Content-Language
Debugging workflow (recommended)
- Paste request URL and request/response headers
- Check whether any Vary dimensions are missing in request headers
- Re-check overall policy with Vary Inspect / Cache Response Analyzer
Operational notes
- Real cache-key behavior depends on CDN implementation. This tool is an RFC-based estimation.
- For Cookie, Authorization, or custom VCL/Lua logic, validate with vendor-specific behavior.
Referenced specs
- RFC 9111 (HTTP Caching)
- RFC 9110 (Vary)
FAQ
Is Vary:* acceptable?
Usually avoid it. It effectively prevents practical reuse in shared caches and hurts hit ratio.
Is query string always part of cache key?
Often yes, but many CDNs allow normalization/exclusion rules. Verify your actual edge configuration.
References
Next to view (diagnostic order)
These links are generated from site_map rules in recommended diagnostic order.
- Vary Inspect — Parse Vary and visualize cache variation keys
- Cache Response Analyzer — Judge cacheability from response headers
- HTTP Cache Mismatch — Identify root causes of cache mismatches
- Cache Diagnostic — Run cross-header diagnostics for HTTP caching
- Cache-Control Inspect — Parse and interpret Cache-Control directives
- Cache Control Overview — Summarize how to use Cache-Control/Pragma/Expires together
- Cache Not Working Troubleshooting — Troubleshoot cache-not-working symptoms step by step from headers
- Pragma Cache Inspect — Parse Pragma and inspect legacy cache control behavior
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 Diagnostic — Run cross-header diagnostics for HTTP caching
- Cache Control Overview — Summarize how to use Cache-Control/Pragma/Expires together
- Cache-Control Inspect — Parse and interpret Cache-Control directives
- 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
URL: https://cdn.example.com/api/items?lang=ja&v=1 Vary: Accept-Encoding, Accept-Language