Create account
PerformanceChecked through WebDiag API

HTTP Cache Policy Checker

Enter a page or static asset URL to check explicit cache policy, validators, Vary, and whether the rules fit HTML or hashed static assets.

  • Cache-Control
  • ETag / Last-Modified
  • CDN/browser cache
Online tool

Try the tool

Enter a URL: WebDiag will run a safe network check and show the result.

Network check through backend

For HTTP/SEO tools, the URL is sent to the WebDiag API, where SSRF protection, DNS/IP policy, and redirect limits are applied.

Reviewed: 2026-07-17
01

How to use it

  1. 1

    Paste an HTML, CSS, JS, image, or font URL.

  2. 2

    Run the header check without downloading the response body.

  3. 3

    Review score, cache directives, validators, and Vary policy.

02

What the tool can do

  • Detects static assets by URL/content-type and applies a different evaluation standard than for HTML.
  • Checks Cache-Control, validators, Expires fallback, and Vary: Accept-Encoding.
  • Runs through SafeHttpFetcher with SSRF protection and read_body=false.
03

Common use cases

  • Verify that hashed CSS/JS/fonts use long-lived immutable caching.
  • Find HTML with risky long public caching.
  • Check whether validators exist for revalidation.
04

How it works inside

The final response body is not downloaded; status, final URL, and headers are used.

Static asset heuristics use both URL extension and content-type.

05

Questions and answers

Should every file use max-age=31536000?

No. Long immutable caching is safe for content-hashed assets. HTML and non-personalized pages need rules that account for purge and releases.

Why does Vary matter?

With compression or content negotiation, Vary helps caches avoid mixing incompatible response variants.