Trailing Dot in a URL: Example
I signed my treaty with the Sultan with a single full stop, placed so far to the right that it now lies in Persia.
The short answer
- What it is
- A trailing dot is a period at the very end of a host name, placed right after the top-level domain. In DNS it marks a fully qualified name, and it often resolves to the same site.
- Why it matters
- A server that answers on the dotted host may create a full copy of the site at a different origin. Canonical tags or links that carry the dot can then point search engines at the wrong host.
- How a crawler should report it
- Normalize the host for comparison, but report a warning when a canonical, a link, or a redirect keeps a trailing dot. Show the exact value as written and say whether the dotted host answered 200 or redirected.
- Live examples
/lab/trailing-dot/(positive)
The Full Stop After a Domain Name
A trailing dot at the end of a host name is legal, and it has a real meaning. In the Domain Name System, every full name ends at the root, which is written as a final dot. So example.com. is the complete form of example.com. The short form may have a local search suffix added by a resolver. The dotted form does not. Few people ever type it, but web software must still handle it.
A dotted host usually reaches your site through a mistake. A template may build a canonical tag from a host value that came with a dot. A link can pick up the period at the end of a sentence when text is turned into a link automatically. Someone can also type or share the dotted form on purpose. Since DNS finds the same server, many sites respond with a normal page and never notice.
Browsers treat the dotted host as a different origin. Cookies, local storage, and logins may not carry across, so a user can seem to be signed out. Certificate checks usually strip the dot, but some servers and CDNs reject the request or send the wrong site. Search engines tend to normalize these hosts, though a crawler that does not may see a duplicate site. A canonical tag with a dot sends a confusing signal in either case.
To detect the problem, request your home page with the dot added and read the status and final URL. Then search your canonical tags, sitemaps, and links for a host ending in a dot. To fix it, send a 301 redirect from the dotted host to the plain host at your server or CDN. Compare the Host header after stripping a final dot. Clean the value in the template that printed it. A dot in the path is a separate matter, so handle that as a normal redirect.