In 1998, two graduate students at Stanford University, Larry Page and Sergey Brin, developed "Backrub", a search engine that relied on a mathematical algorithm to rate the prominence of web pages. The number calculated by the algorithm, PageRank, is a function of the quantity and strength of inbound links.[22] PageRank estimates the likelihood that a given page will be reached by a web user who randomly surfs the web, and follows links from one page to another. In effect, this means that some links are stronger than others, as a higher PageRank page is more likely to be reached by the random web surfer.

In May 2014, Instagram had over 200 million users. The user engagement rate of Instagram was 15 times higher than of Facebook and 25 times higher than that of Twitter.[50] According to Scott Galloway, the founder of L2 and a professor of marketing at New York University's Stern School of Business, latest studies estimate that 93% of prestige brands have an active presence on Instagram and include it in their marketing mix.[51] When it comes to brands and businesses, Instagram's goal is to help companies to reach their respective audiences through captivating imagery in a rich, visual environment.[52] Moreover, Instagram provides a platform where user and company can communicate publicly and directly, making itself an ideal platform for companies to connect with their current and potential customers.[53]

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.[citation needed] 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.[3]