HTTP Header Explainer
Understand what a website's HTTP response headers mean, explained in plain language.
The messages behind every page load
Every time a browser loads a page, the server sends back HTTP headers — instructions about caching, security, content type, redirects and more — that you never normally see. This explains what those headers mean in plain terms, so you can make sense of caching behaviour, spot missing security headers, or understand why a page is doing something unexpected.
Provide the headers and each is explained in readable language.
The headers worth caring about
A few headers reward attention. Cache-control and expires decide how long browsers hold onto your files, which directly affects speed and how quickly updates appear. Security headers like content-security-policy and strict-transport-security harden a site against common attacks, and their absence is a common weakness. Content-type tells the browser how to interpret the response. Understanding these turns a cryptic block of headers into a clear picture of how a site behaves.
Frequently asked questions
What are HTTP headers?
Instructions a server sends with every page — about caching, security, content type and redirects — that browsers act on behind the scenes.
Which headers matter most?
Caching headers for speed, security headers like content-security-policy for protection, and content-type for how the response is read.
Is anything uploaded?
No. The explanation happens in your browser.