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Social media
2004 (Facebook) onward· Idea, religion or movement· Communication & computing
Well documentedSolid records, physical evidence or scientific consensus.
Websites and apps where billions of users post, share and follow one another, funded mostly by targeted advertising.
See it on the Technology & Medicine map →How it works
Social media let users post content and follow others, with feeds ranked by computer algorithms and paid for by ads aimed at each user. Early sites included Six Degrees (1997), Korea's Cyworld (1999) and MySpace (2003). Facebook, started at Harvard in February 2004, reached a billion monthly users in 2012 and about 3 billion today. YouTube (2005), Twitter (2006), Instagram (2010) and TikTok (2016–18) followed.
Why it mattered
It gave billions of people a free public voice and turned attention into a sellable product, reshaping news, advertising, politics and how teenagers grow up.
Think of it like
Like a mall with free entry where the real paying tenants are advertisers, renting access to the shoppers' attention.
How we know
Company user reports and securities filings; Pew Research and DataReportal surveys counting about 5 billion user accounts; records such as the 2018 Cambridge Analytica hearings in Congress.
Still unknown or debated
How much social media harms teenagers' mental health, polarizes politics or spreads misinformation is actively debated; studies disagree on cause versus correlation.
Connections (2)
▸World Wide Web led to Social mediaWell documented
The connection
The web made publishing free, but early sites were mostly read-only pages. Around 2004, so-called 'Web 2.0' sites let ordinary users post, comment and connect with friends, helped by broadband and better browsers. Facebook, YouTube and Twitter began as websites; their ad-funded feeds of user content became the template for social media.
When and how
Six Degrees (1997) and Friendster (2002) as websites; Facebook at Harvard, 2004; YouTube in California, 2005; 'Web 2.0' popularized by Tim O'Reilly's 2004 conference.
How we know
Company histories and archived pages in the Internet Archive's Wayback Machine show social networks started as websites before moving to apps.
Debates and open questions
Some argue social media betrayed the web's open design by concentrating it in a few companies' platforms; Berners-Lee himself has made that criticism.
▸Smartphone made ubiquitous Social mediaWell documented
The connection
Social media began on desktop computers, but smartphones, with built-in cameras and constant connection, made it something people check dozens of times a day. Instagram (2010), Snapchat (2011) and TikTok were built for phones first. Facebook, which shifted to mobile from 2012, now earns the vast majority of its ad revenue on phones.
When and how
iPhone 2007 and its App Store 2008; Instagram launched October 2010 as an iPhone-only app; Facebook's mobile pivot under Mark Zuckerberg from 2012.
How we know
Company filings report mobile's share of users and ad revenue; Pew surveys track rising phone-based use, especially among teenagers.
Debates and open questions
Whether smartphones plus social media caused the rise in teenage anxiety and depression after about 2012 is hotly debated among researchers.