Compare HTTP cache directives before and after a change

Compare response-header text that you collected before and after a hosting or deployment change. The worksheet breaks Cache-Control into directives, then compares captured ETag and Expires values. It works only on text pasted here; no URL is requested and it does not recommend a cache policy.

Compare the same resource using the same request method and collection conditions where practical. Paste the response header lines, not a browser screenshot. The parser recognizes field names without regard to capitalization. Directive values are preserved as entered for comparison.

Compare directives Print or save report

Paste at least one Cache-Control, ETag, or Expires field, then compare.

No comparison run yet.

Changing either capture clears the previous report. Compare again before printing or saving so the output matches the current inputs.

How to read the report

Each Cache-Control directive is shown as added, removed, changed, or unchanged. A change means the pasted directive text differs between the two observations; it is not a verdict that the new response is better or worse. ETag and Expires are compared as whole captured values. If a field appears more than once, the report preserves the captured values and flags the duplicate for review.

The parser splits Cache-Control members at commas outside quoted strings, so a quoted extension value containing a comma stays together. It reports malformed or empty members for review and does not try to interpret directive semantics, resolve conflicts, calculate freshness, or identify which intermediary produced a header.

Worked example

The placeholder values above are illustrative, not observations. They produce these kinds of findings: max-age=3600 changes to max-age=600; stale-while-revalidate=30 is added; public remains unchanged; ETag changes; and Expires is present only before. The output compares entered text and does not say what policy to use.

Before relying on a difference

• Check that both captures refer to the same URL, request method, response status, and relevant request headers. A different resource or conditional request can produce different headers.
• Keep the original captures and record when, where, and how you collected them. This tool does not preserve or verify that context.
• Review the full response and your application, CDN, proxy, and browser configuration. A pasted value alone does not identify the cache layer or explain why it changed.
• Consult your service documentation before making changes. Cache directives can interact with other response fields and service-specific rules.

Sources checked November 5, 2026

• RFC 9111: HTTP Caching — defines HTTP cache behavior and Cache-Control directives, including field syntax and directive processing.
• MDN: HTTP caching — explains caching concepts and common response fields such as Cache-Control, ETag, and Expires.
• Redirect response log reader — summarize manually collected status and Location lines; it does not request URLs.
• Website migration checklist — includes a broader before-and-after response-header comparison alongside migration checks.

This local comparison does not fetch, validate, or store a website response. It cannot determine the effect of a header on a particular browser, CDN, or application, and it is not a cache configuration validator.