The (ongoing) need for speed

By Alan Jackson on 21 June 2010

13 years ago Jakob Nielsen wrote an important article stating that one of the most significant factors in web usability is speed.

In the work that we do, designing web applications that are used in developing countries, we have taken this advice very much to heart.

13 years later Jakob Nielsen has felt the need to write a new version of that article again. And I am glad he has! Despite the roll out of broadband web authors are still creating sites that are slow, although for different reasons, according to Jakob.

In the original article Jakob said that large images were the main culprit in causing slow web pages. Now he says, with the advent of broadband, large images are not the main problem.

Interestingly, with the sites we look at and the connection speeds we deal with, large images still are one of the main contributing factors to slow sites.

Jakob now lays the blame on too many fancy widgets.

I would agree with Jakob here. In my experience the size of javascript is now rivalling that of the large images for the sites we're interested in.

The research into user interface response times is as true now as it was back in 1968 when it was done. From Nielsen's article, remember these times:

• 0.1 seconds gives the feeling of instantaneous response — that is, the outcome feels like it was caused by the user, not the computer.
• 1 second keeps the user's flow of thought seamless. Users can sense a delay, and thus know the computer is generating the outcome, but they still feel in control of the overall experience and that they're moving freely rather than waiting on the computer.
• 10 seconds keeps the user's attention. From 1–10 seconds, users definitely feel at the mercy of the computer and wish it was faster, but they can handle it. After 10 seconds, they start thinking about other things, making it harder to get their brains back on track once the computer finally does respond.

A 10-second delay will often make users leave a site immediately.

Now consider the implications of these times in conjunction with your users' connection speed, particularly if they happen to be in the developing world.

(see also our web design guidelines for low bandwidth connections.)