EaseInCubic

EaseInCubic is an interpolation function used in computer graphics, animation, and web development to control the acceleration of motion over time. It is one of several cubic Bézier easing functions and is designed so that an animated property starts slowly and then accelerates toward the end of the transition.

The mathematical definition of easeInCubic as a cubic function is f(t) = t³, where t represents the normalized time parameter that ranges from 0 to 1. At the start of the animation (t = 0) the derivative f′(0) = 0, indicating no initial velocity. As time progresses, the rate of change grows rapidly, reaching the maximum acceleration as t approaches 1.

In web technology, easeInCubic is frequently specified in CSS transitions and animations using the timing function syntax `cubic-bezier(0.55, 0.055, 0.675, 0.19)` or simply as the keyword `ease-in`. JavaScript animation libraries such as GSAP or jQuery animate also expose easeInCubic as a preset. When applied to properties like opacity or transform, the element moves gently at first and then speeds up, producing a more natural feel than linear motion for many UI interactions.

Compared to other easing styles, easeInCubic provides a smooth entry but a steep exit; it does not rebound or decelerate toward the end. This characteristic makes it suitable for entrances, drop-downs, or other actions where a decisive acceleration is desirable. It is less suitable for hover effects or subtle transitions where a softer start and end are preferable.

Common use cases include page load animations, button presses, and expanding panels. Developers often combine easeInCubic with complementary easing functions like easeOutCubic or easeInOutCubic to create complete motion scenarios that accelerate and then decelerate for a balanced effect.