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RAIL

RAIL , an acronym for Response, Animation, Idle, and Load , is a performance model originated by the Google Chrome team in 2015, focused on user experience and performance within the browser. The performance mantra of RAIL is "Focus on the user; the end goal isn't to make your site perform fast on any specific device, it's to make users happy." There are 4 stages of interaction: page load, idle, response to input, and scrolling and animation. In acronym order, the main tenets are:

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RAIL

Response: Respond to users immediately, acknowledging any user input in 100ms or less.
Animation: When animating, render each frame in under 16ms , aiming for consistency and avoiding jank.
Idle: When using the main JavaScript thread, work in chunks for less than 50ms to free up the thread for user interactions.
Load: Deliver interactive content in less than 5 second .

RAIL

See also