Reviews HTTP caching headers (Cache-Control, Expires, ETag, Last-Modified, Vary, Set-Cookie) for pages, assets, APIs. Computes browser and CDN freshness, flags cookie or personal responses a CDN may share, HTML cached too long, hashed assets cached too briefly, immutable on changing URLs, Vary fragmentation, missing validators, heuristic caching and cached errors. Suggests a header per resource. Includes a stdlib Python checker with --self-test.
