Definition

Link shortener

A link shortener wraps a long URL in a compact one (bit.ly, tinyurl, geni.us) that redirects to the original. In affiliate chains, shorteners add a hop that can rate-limit, expire, or be deleted independently of the affiliate link inside.

Shorteners are also opaque: nobody — including you, a year later — can tell what's inside one without expanding it. Serious link audits expand every shortener first, then judge the underlying affiliate link. Aggressive rate limiting (geni.us especially) also means automated checkers must pace their requests or misread throttling as breakage.