We know that users prefer websites and applications that work fast. There is a lot of evidence that link performance to revenue. Let’s see what are main parts of the user experience that relate to the perception of ‘speed’ and how we can improve it.
RAIL performance model
RAIL is a user-centric performance model. Every web app has these four distinct aspects to its life cycle, and performance fits into them in very different ways. You can see in the image below the 4 main aspects and what are the time limits to each stage.
- Focus on the user – the end goal isn’t to make your site perform fast on any specific device, it’s to ultimately make users happy.
- Respond to users immediately – acknowledge user input in under 100ms – In mobile always use touch events and not click events (yep, click events still got this 300ms delay on mobile browsers)
- Render each frame in under 16ms and aim for consistency. Users notice “jank” because in most cases it will ‘jump’ to their eyes.
- Keep users engaged – deliver interactive content in under 1000ms.