A free social bookmarking service is a centralized online service which enables users to add, annotate, edit, and share bookmarks of web documents. Many online bookmark management services have launched since 1996, and the terms social bookmarking and tagging were popularized by a social bookmarking service founded in 2003. Tagging is a significant feature of free social bookmarking systems, enabling users to organize their bookmarks in flexible ways and develop shared vocabularies.

These bookmarks can be found on social bookmarking lists, which are lists of bookmarks compiled by web users based on popularity, topic, and other factors. These free social bookmark lists allow you to find pages you want to bookmark, or pages that others have bookmarked.

Free social bookmarking is different from File sharing. Free social bookmarking does not save the resources themselves, merely bookmarks that reference them, such as providing a free link to the bookmarked page. Descriptions may be added to these bookmarks in the form of metadata, so users can understand the content of the resource without needing to download it for themselves first. These bookmarks are usually public, but can also be saved privately, or shared only with specified people or groups, or shared only inside certain networks. The allowed people can usually view these social bookmarking lists chronologically, by category or tags, or through a search engine.

Most free social bookmark services encourage users to organize their bookmarks with informal tags instead of the traditional browser based system of folders. They also enable viewing social bookmarking lists associated with a chosen tag, and include information about the number of users who have bookmarked them.

Many free social bookmarking services provide web feeds for their free social bookmarking list, including social bookmarking lists organized by tags. This allows subscribers to become aware of new bookmarks as they are saved, shared, and tagged.