What is two way link building

[har.sinha]

A two-way link refers to a website linking to you and you linking back to it. This is often a result of link exchanges and this is the reason why search engines see two-way links as less valuable. If the only reason a link is present on a website is to boost the recipient site’s rankings, there’s little benefit to it.

[amanshastry43]

Two-way link building is a technique of reciprocal exchanges between two sites intended to be beneficial to both, search engines consider this to search manipulation in violation of their guidelines when it's between 2 unrelated sites.