What is AJAX?

AJAX is one of the current buzzwords in Web design and development, but what does it mean and what can it actually do?

The name AJAX is short for 'Asynchronous JavaScript And XML'. It isn't a new technology but a term that refers to a group of existing web technologies that can be brought together to offer users a richer and more responsive experience when they visit a web site. So how does it do this?

Whenever a user first visits a web page he has to wait for the whole page (text, images, Flash animations, etc) to download before he can see it in its entirety - everything is downloaded together (synchronously) from the page's web server. This is still the case but the difference using AJAX comes when the user wishes to update some data on the page, perhaps by clicking on a button or link. Normally, this kind of action means that the whole page will need to be reloaded again to update what might only be a small amount of content - and even in these days of fast internet connections there will be a perceptible delay (more obvious during busy periods) while the whole page is downloaded again from the server.

This whole process makes web applications feel much less smooth and responsive than desktop programs, but AJAX has come along to help out. By using fairly simple AJAX programming techniques web pages can now be updated without the need for a full page refresh. Instead, when a user chooses some interactivity a single request is sent on its own (asynchronously) to the web server and the page is updated without the rest of the content being re-sent as well, making the whole update quicker, more efficient and more enjoyable.

Click the button to see AJAX in action: