Performance Tools

Cache Headers Checker

Analyze a website's caching headers - Cache-Control, Expires, ETag, Last-Modified, and Age.

Enter a domain to analyze its caching headers.

More Performance Tools

HTTP Version Checker Keep-Alive Checker Brotli Compression Checker Page Size Checker GZIP Compression Checker CDN Detection Image Optimization Checker Performance Health Score

JustChecker tracks your website's performance signals continuously.

What Is the Cache Headers Checker?

Caching headers tell browsers and CDNs how long they may reuse a response. This tool shows a page's Cache-Control, Expires, ETag, Last-Modified and Age headers.

When to Use It

When repeat visits are slow.
When visitors see outdated content after an update.
When configuring a CDN.

How to Use It

Enter the URL.
Review the caching headers and their values.

Understanding the Result

Versioned static files (such as app.css?v=123) can use Cache-Control: public, max-age=31536000, immutable. HTML is usually no-cache or a short max-age so updates show quickly. An Age header means the response came from a CDN or proxy cache.

Limitations

This checks the URL you enter; images, CSS and scripts can have different rules, so check their URLs too.

Frequently Asked Questions

Cache-Control is the modern, more flexible directive (supporting fine-grained rules like max-age and no-cache); Expires is an older, simpler date-based header - when both are present, Cache-Control generally takes precedence in modern browsers.

An ETag is a unique identifier for a specific version of a resource - it lets a browser ask "has this changed since I last saw ETag X?" and receive a lightweight "not modified" response instead of re-downloading unchanged content.

Frequently-updated content (a homepage, an API response) benefits from short or no caching so visitors always see current data; static assets that rarely change (a versioned CSS/JS file, a logo) benefit from long caching to avoid unnecessary re-downloads.

Despite the name, no-cache doesn't forbid caching - it means the cached copy must be revalidated with the server before being reused; "no-store" is the directive that actually prevents caching entirely.

It reports how long (in seconds) a cached response has been sitting in an intermediate cache (like a CDN) before being served to you - a high Age value confirms caching is actively working as configured.

Yes - overly aggressive caching (a long max-age on content that changes frequently) is a common, real cause of visitors seeing stale versions of a page after an update, until their cached copy naturally expires.