FREE TOOL / NO ACCOUNT / RUNS ON THE PAGE YOU GIVE IT
HTTP header checker
Every response header from any URL, scored on transport, browser safety, caching and crawlability, with one plain line on what each header actually does.
One request, redirects followed. We report the response headers of the page you end up on, with a line on what each one does.
QUESTIONS ABOUT THIS TOOL
- Which security headers actually matter?
- Four carry most of the weight: Strict-Transport-Security so the first request of a session cannot go over http, Content-Security-Policy so injected script has nowhere to load from, X-Frame-Options or a frame-ancestors directive so nobody can frame your page and steal clicks, and X-Content-Type-Options: nosniff so the browser cannot guess a file into being script.
- Why does X-Robots-Tag matter for SEO?
- It does the same job as a meta robots tag, but in a header, so it never appears in the page source. A noindex delivered this way removes a page from search and is invisible to anyone reading the HTML, which is why it can sit unnoticed for months.
- What is a cache validator?
- An ETag or a Last-Modified header. It lets a returning browser ask whether anything changed and receive a 304 with no body, instead of downloading the whole page again. Without one, every revalidation is a full transfer.
- Why flag the Server header?
- Only when it carries a version number. Knowing you run a specific version tells an attacker which published exploits to try first. Naming the software without a version is normal and is not flagged.
- Do you check the headers of the URL I typed, or the one it redirects to?
- The one it redirects to. Headers on a 301 belong to the redirect, not to the page, so we follow the chain and report the destination. The number of hops is shown alongside.
A TOOL CHECKS ONCE. SEOBUILDER KEEPS WATCH.
We can watch this for you.
Headers change when someone changes a CDN rule, and nothing in the page looks different. We check yours on a schedule and tell you when a security header disappears or an X-Robots-Tag starts saying noindex.