How Fast is Fast Enough?

Kyle Gentry

How Fast is Fast Enough?

As a company focused on web performance, we get asked all the time: "How fast should my site load?" One way we help answer this question with customers is by running tests to see where bounce rates start to increase and conversions decrease for their specific users. While helpful, these tests are time-consuming and quite difficult to administer properly.

Thankfully, we recently read an article by Denys Mishunov at Smashing Magazine that looks at this question from a completely different perspective – human psychology – that is a nice rule of thumb when considering your site's load times. Within his analysis, he breaks down time into four categories:

  1. Instant (0.1-0.2 seconds) is when there is no perceptible "lag" in response. For example, when clicking a button on a website, the button should depress instantly to mirror the pressing of a button in real life.
  2. Immediate (0.5-1s) is the time a user expects a reaction but not necessarily a response. A prime example would be the acknowledgement (a nod, perhaps) that you are hearing someone when they are talking to you.
  3. User Flow (2-5s) is the time when the person is most likely to experience "concentration, absolute absorption in an activity and deep enjoyment." Delivering information within this time frame gives it the best chance of being consumed.
  4. Attention Span (5-10s) is the time a user is increasingly likely to become distracted and disengaged.


Now, of course we would all like websites to load instantly or immediately, but unfortunately, there are many variables that make such a goal unrealistic. However, if you look at the definitions, you can apply some rules to page load times that are achievable and can maximize the likelihood that you will get and maintain user attention:

1. Start Render should be Immediate

Start render, or the first time something is displayed on the screen, should take place in under one second. When users click on a link or type in a URL, they expect an immediate visual response that the page is loading. The longer a user stares at a blank screen, the more likely they are to bounce.

2. Pages should load in under 5 seconds

While it is still possible that a user will wait longer than 5 seconds for a page to load, knowing what we know about shrinking human attention spans (apparently goldfish now have longer ones than we do?) you are likely to start to lose users each second over 5. But if user patience is not static and continues to get worse, this begs the question: Should we "skate to where the puck is going to be?" If so, where is the puck headed?

We believe 3 seconds is the new 5 seconds

If we assume that social and other mobile mediums will increasingly influence Internet traffic and that those mediums tend to bring some of the least patient users, we believe 3 seconds should be the goal. That is why we have adopted a mission of delivering all sites to all users in under 3 seconds. We believe it is what users will expect in the very near future.

One additional piece of information in the article that we found interesting had to do with perceived performance improvements. Essentially, performance improvements under 20% are not perceptible to humans. Said differently, for your users to notice performance improvements on your site, you will need to reduce that load time by 20% +. So if your site loads in 6s for a user, you would need to reduce it to 4.8s or less for that same user to notice the difference. This can be helpful when selecting and prioritizing performance optimizations. If a change, or series of changes, isn’t going to improve performance by 20% or more for all or a subset of users, it might not be worth the effort.

Coincidentally, when we set up our Performance Guarantee, we made it 20% faster or free. Turns out we were onto something.


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