A Link Rot Bestiary/Chapter 2 : Hard and Crunchy 404

Dead link or Hard 404 is link that is unambiguously dead. The status code might also be 403, 400, etc.. it might be the domain no longer exists on the Internet, in which case it might return no status code at all. It might be a status code such as 5xx. Dead links are traditionally how link rot is measure and determined, and account for the largest percentage of inoperable links.

Soft 200 or False 400 are links that present themselves as being dead, but are actually still live. The most common example are bot blockers which are policy blocks, such as CloudFlare, which detect and block bot activity. They may be return status codes in the 4xx and 5xx range. Nevertheless the page is still viewable through normal web browsing.

Crunchy 404 is a link that is ambiguous, falling somewhere between a hard 404 and a soft 404. The content is different from the original page, but it still has content relevant to the original. Depending on what information the reader seeks, it could be considered a dead link, or a live link, relative to the viewer. This is also the realm of content drift, where content on the page "drifts" over time, the extent of which determine if the page is considered dead or not.