Response Animation Idle Load (RAIL)

Response Animation Idle Load (RAIL) is a concept which is trending since 2015, but now we are sure that it will exist in 2019 and beyond. It is basically designed to achieve excellent performance of the website with quick loading time.

The RAIL concept is for the web designers who aim to build a customer-centric website with exceptional user experience. The RAIL excels UX in every aspect such as scroll, drag, tap, etc. and provides structure necessary for brilliantly performance.

When we are talking about performance the main issue that we face is that there are various ways of measuring it and everyone asks the same question to their self that do we measure the speed index or initial load time. Matter of fact there are various potential metrics and each of us has their preferences.

RAIL is the concept considers various context of user interaction on the website, instead of targeting on single performance metric. For example once something is loaded, clicked or scrolled. Each of these context aims for different performance goals, as the user expectation might vary from context to context.

RAIL (Response, Animation, Idle, and Load) these are the four distinct ways to explain user actions.


This determines how quickly one receives a response after inserting an input. The goal would be to deliver the feedback in less than 100ms, once a user does a click or a tap on a button or icon. Overall, it should feel like an immediate response on your input.


This involves scrolling, visual animation and dragging. The only aim would be to complete frame within 16ms, which would allow the animation to sustain the ideal rate of 60fps. 


This describes the process working in the background, especially the process which doesn’t require loading. Normally the process would be grouped in to blocks in less than 100ms or 50ms. Once user starts interacting with the page, the main goal would be to keep 100ms response rate while other actions are being performed in the background.


This defines how quickly one can achieve the first meaningful paint; normally it is expected to be less than one second. Once paint received, the only aim would be to sustain the responsive rate of an application for the user.

These are some freely available tools to measure and track the goals set by RAIL and webpage test.

Chrome DevTools

Chrome’s in-built developer tools allowyou to conduct in-depth analysis of every process while your page runs or loads. You get specific instructions on the usage of DevTools to mesure RAIL metrics.


Lighthouse is an amazing audit tool which is available in Chrome DevTools as a browser extension and it normally runs various audits and gives you a report of your website’s performance. Demonstrating you if your website performance meets the best practices, accessibilities and SEO.


This is basically a speed testing tool and you have to just enter a URL to test. One can also use advance settings to choose a mobile device and a slow connection to evaluate RAIL’s loading guidelines.

Overall, RAIL provides a frame work that focuses on the overall user experience, providing developer reliable benchmark for measuring and improving website performance.