What is the 3 second rule in website design?

The rule is used in two overlapping ways. One is about speed: the page should load in under three seconds. The other is about clarity: within the first few seconds of seeing the page, a visitor should understand what you do and whether you can help them. Neither is a law, but both point at the same thing, which is that people judge quickly and leave easily.

The speed figure most often quoted comes from Google. Its 2016 research into mobile sites found that 53% of mobile visits were abandoned if a page took longer than three seconds to load. That data is several years old and phones and networks have improved since, so treat the exact number with care. The direction has not changed: slower pages lose more visitors.

For a trades business, the clarity half of the rule matters just as much. Someone with a leaking pipe wants to see your trade, your area and your phone number without scrolling. If the first screen is a large stock photo and a vague slogan, a fast load time does not save you.

To check your own site, open it on your phone using mobile data rather than wifi, and count. Then ask someone who does not know your business to look at the first screen for three seconds and tell you what you do and where. Free tools such as Google's PageSpeed Insights will show what is slowing a page down.