A broken link (also known as a dead link) is a link within a target website that points to a web page that returns HTTP 404, and has become permanently unavailable.
In Ahrefs Site Explorer, we have a 'Broken links' report which shows all the outbound broken links together with their anchor texts that were found within a target website.
Note that a broken link can be both internal (pointing to another page of the same domain) or external (pointing to a web page within another domain).
A link can become broken for a variety of reasons such as the page has been moved, the domain expired, etc. That’s why in the 'Broken links' report, each link is marked with a red tag that specifies the issue — for instance, '404 not found' or 'cannot resolve host'.
It’s recommended to fix broken links of your own website for better user experience.