A web search tool compiled manually by human editors. Once websites are submitted with information such as a title and description, they are assessed by an editor and, if deemed suitable for addition, will be listed under one or more subject categories. Users can search across a directory using keywords or phrases, or browse through the subject hierarchy. Best examples of a directory are Yahoo and the Open Directory Project.

Directories have become a very popular tool for Search Engine Optimization. Inbound links are a necessary component of any SEO campaign. Many webmasters aren't keen on the idea of attempting to convince other webmasters to manually add their links in an exchange agreement. Many Emails go unanswered for this kind of an agreement.

Directories offer streamlined link exchange functionality. Webmasters can visit, navigate to their appropriate category, add the details of their link, link to the directory site, verify automatically that they've added the link and wait usually no longer than two weeks for directory editors to include their link. For this reason directories have sprung up all over the internet and show no sign of diminishing in popularity.