A web directory or link directory is a directory on the World Wide Web. It specializes in linking to other websites and categorising those links.
A web directory is not a search engine and does not display lists of web pages based on keywords, instead it lists web sites by category and subcategory. The categorisation is usually based on the whole web site, rather than one page or a set of keywords, and sites are often limited to inclusion in only one or two categories. Web directories often allow site owners to directly submit their site for inclusion, and have editors review submissions for fitness.
RSS directories are similar to web directories, but contain collections of RSS feeds, instead of links to websites.
A link from a web directory has two benefits.
The first is that the search engines will consider a link from any website to yours as a vote for your website. The higher the Page Rank of the site linking to yours, the greater the value of the vote. Websites with greater vote counts and link quality appear higher in search engine results. The second benefit is that the visitors to the web directory may follow the link and land on your website.
This second benefit is greater in bid for position web directories than in traditional web directories as the highest paying links are more visible. Either on the homepage, or at the top of the chosen category. In traditional web directories links can often be buried several pages into a category and have poor visibility. Webmasters wishing to pay high bid quantities can easily increase their listings visibility by pushing their listing to the top of the list.
Some directories are very general in scope and list websites across a wide range of categories, regions and languages. But there are also a large number of niche directories, which focus on restricted regions, single languages, or specialist sectors.
Examples of well known, general, web directories are Yahoo! Directory and the Open Directory Project (ODP). ODP is significant due to its extensive categorization and large number of listings and its free availability for use by other directories and search engines.
Directories have various types of listings, often dependent upon the price paid for inclusion:
Free Submission - there is no charge for the review and listing of the site
Reciprocal Link - a link back to the directory must be added somewhere on the submitted site in order to get listed in the directory
Paid Submissions - a one-time or recurring fee is charged for reviewing/listing the submitted link
No Follow - there is a rel="nofollow" attribute associated with the link, meaning search engines will not follow the link
Featured Listing - the link is given a premium position in a category (or multiple categories) or other sections of the directory, such as the homepage
Bid for Position - where sites are ordered based on bids
Affiliate Links - where the directory earns commission for referred customers from the listed websites