Performance Tools

Cache Headers Checker

Check the caching rules a website sends to browsers and CDNs.

Not sure what to enter? Try an example: wikipedia.org

Free & instant No signup How to use FAQ

Enter a URL to read its Cache-Control, Expires, ETag, Last-Modified and Age headers and see how long the response may be cached.

What are cache headers?

Cache headers - Cache-Control, Expires, ETag, Last-Modified and Age - tell browsers and CDNs whether and for how long they may reuse a response. Good caching makes repeat visits much faster and reduces server load; missing or no-store headers make every visit download everything again.

How to check caching headers

Enter the domain or URL in the box above.
Click Check Cache Headers.
Review Cache-Control and the validators (ETag/Last-Modified).
Give static files (CSS, JS, images) long max-age values with versioned file names, and keep HTML short-lived.

Related checks

To see whether a CDN serves cached copies, use CDN Detection.
To see every header, use the HTTP Headers Checker.

Give versioned files such as CSS, JavaScript and images a long max-age, and keep HTML short so updates appear quickly. JustChecker measures load times over weeks so you can see whether caching helps.

Frequently Asked Questions

Images, CSS and JavaScript with versioned names: up to a year (max-age=31536000). HTML pages: short or no-cache, so visitors always get fresh content.

They let the browser ask "has this changed?" and get a tiny 304 Not Modified reply instead of downloading the file again.

How many seconds the response has been sitting in a CDN or proxy cache. A value above zero means the page was served from cache, not your server.

Share this tool:

Need a website for your business? Only $599