Redirect checker

What a redirect does

A redirect sends anyone who asks for one address to another. The status code says what kind: 301 and 308 mean moved for good; 302, 303 and 307 mean moved for now. Google's documentation is direct about the difference: with a permanent redirect "the indexing pipeline uses the redirect as a signal that the redirect target should be canonical"; with a temporary one it does not (Google: redirects).

What this checker looks for

• Chains. Two or more redirects in a row. Google's crawling guidance says to avoid long redirect chains, "which have a negative effect on crawling" (Google: crawl budget), and each hop is a wasted round trip for a visitor.
• Loops. A chain that comes back on itself and never reaches a page. Browsers show an error.
• Temporary redirects on permanent moves. A 302 left in place for years keeps the old address as the one Google treats as real.
• http and www. A site can be reached four ways: http or https, with or without www. To Google those are four addresses, so all of them should end up at one. Google prefers HTTPS pages as canonical.
• Meta refresh. A redirect done inside the page rather than by the server. Google follows it, but a server redirect is clearer.

We follow up to 10 hops, the same limit our crawler uses.

Next: check the HTTPS certificate, or see the response headers.