In 2004, Tim O’Reilly codified the term 'Web 2.0' to describe a seismic shift from static brochure websites to dynamic, user-generated web applications powered by asynchronous client-side requests and open data exchange.
1. Jesse James Garrett and the AJAX Paradigm
Before Asynchronous JavaScript and XML (AJAX), every user click triggered a full white-screen page reload. The introduction of XMLHttpRequest in Google Maps and Gmail enabled smooth, app-like desktop experiences directly inside the web browser.
2. RSS and Atom: The Decentralized Web Ecosystem
Really Simple Syndication (RSS) empowered users to curate their own reading feeds across thousands of independent blogs and news portals without intermediary algorithmic feeds.
3. RESTful Open APIs and Mashup Culture
The mid-2000s celebrated 'API mashups'—developers combining Flickr photo streams, Twitter firehoses, and Google Maps layers into novel creative web services.
4. Folksonomy and User-Generated Tagging
Platforms like Delicious and Flickr replaced rigid hierarchical taxonomies with decentralized tagging (*folksonomies*), organizing knowledge organically through collective user curation.
5. From Open Protocols to Platform Enclosure
The tragic closing of open APIs in the 2010s transformed the collaborative web into siloed corporate walled gardens, inspiring today's Fediverse and decentralized web movements.
Architectural Insight
Web 2.0 succeeded because it treated the browser as a universal application runtime and the user as a co-creator.