Who is using Ajax?
According to Alexa, the top international web brands are Yahoo, Microsoft, Google, MySpace, EBay, YouTube, Amazon, Wikipedia and the BBC. These 8 brands own the top 13 websites by page views.
None of these sites is JavaScript-free.
The BBC, EBay, Wikipedia and MySpace all take a "Progressive Enhancement" approach (create a JavaScript free site first then add tweaks). This approach is good for large sites that wish to "keep-up" but are not looking to the user interface to drive additional value to the site. It is rumoured that MySpace are planning a UI rewrite that will make much heavier use of Ajax. Amazon uses this approach for it ratings widget throughout its main site and for its A9 search site. Microsoft uses this approach on its home page, and Google for Google News.
The "Second Site" approach means creating a JavaScript based site first and then porting it to work with scripting turned off. It is generally a better way to achieve a rich site since it treats the majority case first (90-95% of users have scripting enabled). Google have taken this approach with Google Maps, GMail, Google Calendar and others. Amazon uses it for its diamond search site. Microsoft use it for Live Search.
The "Accessible JavaScript" approach means rejecting browsers that can not support JavaScript and aiding JavaScript compatible screen readers to make the site accessible. Google uses this approach for Google Spreadsheets, Writely Word Processor, Web Page Creator, Blog Reader, Customized Homepage and other products. Microsoft uses it for MSN Virtual Earth, and Image Search. Perhaps the most surprising is the well established Yahoo Mail, which appears to adopting a JavaScript only approach. Yahoo also uses this approach on their new Maps site. Virtually the entire YouTube site requires JavaScript.
This is a short subset of the Ajax based applications created by these companies. For example, the complete list of Google applications is much longer and virtually all these applications use JavaScript in some way, including Google accessible search – a site designed for use with screen readers.
Developer Libraries
There are 2 types of Ajax library; client-side UI libraries, which are JavaScript based and server based libraries to help browser/server integration. It is common to use both types of library in a significant application.
According to research by the Burton Group (summarized here and here), the most popular client-side libraries are Prototype/Scriptaculous (45%) and Dojo (19%) while the most popular Java based interaction libraries are DWR (53%), GWT (15%) and AjaxTags (7%). It is common to use a client side library in conjunction with a server interaction library, for example Scriptaculous + DWR.
