Recently, rich Internet application techniques such as Ajax, Adobe Flash, Flex, and Silverlight have been developed to improve browser-based applications. These technologies allow a Web page to request an update for some part of its content and to alter that part in the browser, without needing to refresh the whole page at the same time.

Web 2.0 is like an improved version of the World Wide Web. Technologies such as weblogs (blogs), social bookmarking, wikis, podcasts, RSS feeds (and other forms of many-to-many publishing), social software, and Web application programming interfaces (APIs) advance beyond read-only Web sites. Stephen Fry (actor, author, and broadcaster), who writes a technology column in the British Guardian newspaper, describes Web 2.0 as "... an idea in people's heads rather than a reality. It’s actually an idea that the reciprocity between the user and the provider is what's emphasised. In other words, genuine interactivity, if you like, simply because people can upload as well as download."

Ajax allows Web sites to mimic personal computer applications, such as word processing, spreadsheets, and slide show presentations. WYSIWYG wiki sites replicate many features of PC authoring applications. Still other sites perform collaboration and project management functions, like the well-known Writely, owned by Google, Inc. since 2006.

Web 2.0 has allowed static information-only Web sites to become interlinked computing platforms that function like locally-available software. Web 2.0 includes a social element where users generate and distribute content, often with freedom to share and re-use. This can allegedly result in a rise in the economic value of the Web as users do more online

The sometimes complex and continually evolving technology infrastructure of Web 2.0 includes server software, content syndication, messaging protocols, standards-oriented browsers with plugins and extensions, and various client applications. These different but complementary approaches provide Web 2.0 sites with information storage, creation, and dissemination challenges and capabilities that go beyond the original Web.

Web 2.0 sites typically include some of the following features/techniques:

* Rich Internet application techniques, often Ajax-based
* Semantically valid XHTML and HTML
* Microformats extending pages with additional semantics
* Folksonomies (in the form of tags or tagclouds, for example)
* Cascading Style Sheets to aid in the separation of presentation and content
* REST and/or XML- and/or JSON-based APIs
* Syndication, aggregation and notification of data in RSS or Atom feeds
* Mashups, merging content from different sources, client- and server-side
* Weblog-publishing tools
* Wiki or forum software, etc., to support user-generated content