Checker tools

Verify that a site, file or address is set up the way you think it is

A checker answers a yes-or-no style question and shows the evidence. Does this URL redirect somewhere unexpected? Does the page send the security headers browsers look for? Is the robots.txt file readable, and does the sitemap list working pages? These are audits you would otherwise run with several command-line tools.

Site owners and SEO specialists use the meta tag, sitemap, robots.txt, favicon and broken link checkers before and after a launch. Security-minded users test password strength, HSTS preload status, mixed content and whether a link is flagged as unsafe. Email teams validate an address before adding it to a list.

Several checkers must contact the address you enter, so they work only on public sites and cannot inspect pages behind a login or on your private network. Results describe the moment you ran the check, and it is worth repeating after any configuration change. When a result looks surprising, compare it with a second tool or a manual check before you edit production settings.

Common questions

Why can a checker not reach my staging site?

Checkers that fetch a URL run from a public server, so they cannot open pages behind a login, a VPN or a private address. Test staging environments with your browser's developer tools or a local command-line client instead.

Does a broken link result always mean the link is broken?

Not always. Some sites block automated requests or respond slowly, which can look like a failure. Open any flagged link in a browser to confirm before you edit or remove it.

How does the email validator work?

It checks that the address is well formed and that the domain can plausibly receive mail. It cannot confirm that a specific mailbox exists, because only a delivery attempt or a confirmation message proves that.