Websites such as Delicious, Digg, Slashdot, Diigo, Stumbleupon, and Reddit are popular social bookmarking sites used in social media promotion. Each of these sites is dedicated to the collection, curation, and organization of links to other websites that users deem to be of good quality. This process is "crowdsourced", allowing amateur social media network members to sort and prioritize links by relevance and general category. Due to the large user bases of these websites, any link from one of them to another, the smaller website may in a flash crowd, a sudden surge of interest in the target website. In addition to user-generated promotion, these sites also offer advertisements within individual user communities and categories. Because ads can be placed in designated communities with a very specific target audience and demographic, they have far greater potential for traffic generation than ads selected simply through cookie and browser history. Additionally, some of these websites have also implemented measures to make ads more relevant to users by allowing users to vote on which ones will be shown on pages they frequent. The ability to redirect large volumes of web traffic and target specific, relevant audiences makes social bookmarking sites a valuable asset for social media marketers.
Optimizing a website may involve editing its content, adding content, modifying HTML, and associated coding to both increase its relevance to specific keywords and to remove barriers to the indexing activities of search engines. Promoting a site to increase the number of backlinks, or inbound links, is another SEO tactic. By May 2015, mobile search had surpassed desktop search.