After registering to use the site, users can create a user profile, add other users as "friends", exchange messages, post status updates and photos, share videos, use various apps and receive notifications when others update their profiles. Additionally, users may join common-interest user groups, organized by workplace, school or college, or other characteristics, and categorize their friends into lists such as "People From Work" or "Close Friends". Also users can complain or block unpleasant people. Facebook had over 1.18 billion monthly active users as of August 2015. Because of the large volume of data users submit to the service, Facebook has come under scrutiny for their privacy policies. Facebook, Inc. held its initial public offering in February 2012 and began selling stock to the public three months later, reaching an original peak market capitalization of $104 billion. On July 13, 2015, Facebook became the fastest company in the Standard & Poor's 500 Index to reach a market cap of $250 billion. Following its Q3 earnings call in 2015, Facebook's market cap soared past $300 billion.

Registered users can read and post tweets, but those who are unregistered can only read them. Users access Twitter through the website interface, SMS or mobile device app. Twitter Inc. is based in San Francisco and has more than 25 offices around the world.

Twitter was created in March 2006 by Jack Dorsey, Evan Williams, Biz Stone, and Noah Glass and launched in July 2006. The service rapidly gained worldwide popularity, with more than 100 million users posting 340 million tweets a day in 2012. The service also handled 1.6 billion search queries per day. In 2013, Twitter was one of the ten most-visited websites and has been described as "the SMS of the Internet". As of May 2015, Twitter has more than 500 million users, out of which more than332 million are active.

In 2006, LinkedIn increased to 20 million members. As of October 2015, LinkedIn reports more than 400 million acquired users in more than 200 countries and territories.

The site is available in 24 languages, including Arabic, Chinese, English, French, German, Italian, Portuguese, Spanish, Dutch,Swedish, Danish, Romanian, Russian, Turkish, Japanese, Czech, Polish, Korean, Indonesian, Malay, and Tagalog.As of 2 July 2013, Quantcast reports LinkedIn has 65.6 million monthly unique U.S. visitors and 178.4 million globally, a number that as of 29 October 2013 has increased to 184 million. In June 2011, LinkedIn had 33.9 million unique visitors, up 63 percent from a year earlier and surpassing MySpace. LinkedIn filed for an initial public offering in January 2011 and traded its first shares on May 19, 2011, under the NYSE symbol "LNKD".

Google was founded by Larry Page and Sergey Brin while they were Ph.D. students at Stanford University. Together they own about 14 percent of its shares but control 56 percent of the stockholder voting power through supervoting stock. They incorporated Google as a privately held company on September 4, 1998. An initial public offering followed on August 19, 2004. Its mission statement from the outset was "to organize the world's information and make it universally accessible and useful," and its unofficial slogan was "Don't be evil". In 2004, Google moved to its new headquarters in Mountain View, California, nicknamed the Googleplex. In August 2015, Google announced plans to reorganize its interests as a holding company called Alphabet Inc. When this restructuring took place on October 2, 2015, Google became Alphabet's leading subsidiary, as well as the parent for Google's Internet interests.

Rapid growth since incorporation has triggered a chain of products, acquisitions and partnerships beyond Google's core search engine (Google Search). It offers online productivity software (Google Docs) including email (Gmail), a cloud storage service (Google Drive), an office suite (Google Docs) and a social networking service (Google+). Desktop products include applications for web browsing (Google Chrome), organizing and editing photos (Picasa and Google+ Photos/Google Photos), and instant messaging(Hangouts). The company leads the development of the Android mobile operating system and the browser-only Chrome OS^[ for a class of netbooks known as Chromebooks. Google has moved increasingly into communications hardware: it partners with major electronics manufacturers in the production of its "high-quality low-cost" Nexus devices. In 2012, a fiber-optic infrastructure was installed in Kansas City to facilitate a Google Fiber broadband service.

The corporation has been estimated to run more than one million servers in data centers around the world (as of 2007). It processes over one billion search requests and about 24 petabytes of user-generated data each day (as of 2009). In December 2013, Alexa listed google.com as the most visited website in the world. Numerous Google sites in other languages figure in the top one hundred, as do several other Google-owned sites such as YouTube and Blogger. Its market dominance has led to prominent media coverage, including criticism of the company over issues such as aggressive tax avoidance, search neutrality, copyright, censorship, and privacy.

Most of the content on YouTube has been uploaded by individuals, but media corporations including CBS, the BBC, Vevo, Hulu, and other organizations offer some of their material via YouTube, as part of the YouTube partnership program. Unregistered users can watch videos, and registered users can upload videos to their channels. Videos considered to contain potentially offensive content are available only to registered users affirming themselves to be at least 18 years old.