Exact-match anchor
An exact-match anchor is link text that is exactly the keyword the target page wants to rank for, such as "buy running shoes" pointing to a running shoes page.
An exact-match anchor is the most aggressive form of anchor text because it tells search engines, in the bluntest possible way, what query the linked page should rank for. A small number of relevant exact-match anchors can reinforce a page's topic, which is why they remain part of a natural profile.
The risk is concentration. Because natural editorial links rarely use a perfect keyword phrase, a profile heavy with exact-match anchors is a strong over optimization signal and is exactly the pattern google penguin was built to detect. Over-using them can trigger a manual action or an algorithmic suppression rather than a boost.
As a rule of thumb, keep exact-match anchors a small minority of your profile and let branded anchor, naked url anchor, and partial match anchor text dominate. When you do control the anchor (a paid placement or guest post), resist the temptation to use the exact keyword every time. There is no universal safe percentage, so model your ratios on healthy competitors rather than a fixed target.