CSS Animation Builder

Overview

The CSS Animation Builder assembles a @keyframes block and the matching animation: shorthand from a sequence of keyframe steps, plus duration, easing, delay, iteration count, direction, and fill mode. Pick named keyframes or define percentages manually, then copy CSS that drops into any stylesheet.

Useful when learning how to write CSS keyframe animations or how to build a CSS animation shorthand, and when designers and front-end developers want to prototype motion without hand-typing the verbose @keyframes syntax. Reach for it building loading spinners, micro-interactions, and section reveal effects.

How it works

CSS animations consist of a @keyframes rule that lists waypoints (from, to, 0%, 50%, 100%) and an element rule that binds the animation name to a duration, timing function, and other properties via the animation shorthand. Browsers interpolate between the listed keyframes using the timing function; properties not listed at every step animate from their declared value on the element.

The builder validates the shorthand order (duration before delay), ensures both from/to are present when needed, and emits prefix-free modern syntax. It also surfaces animation-fill-mode because forgetting forwards is the classic reason an animation snaps back at the end.

Examples

• A fade-in animation: @keyframes fade-in { from { opacity: 0; } to { opacity: 1; } } with animation: fade-in 400ms ease-out 100ms forwards;.
• A pulsing dot uses 0% { transform: scale(1); } 50% { transform: scale(1.4); } 100% { transform: scale(1); } with animation: pulse 1.2s ease-in-out infinite;.
• A slide-up with transform: translateY(20px) at 0% and translateY(0) at 100%, plus forwards fill mode.
• A spinner uses animation: spin 1s linear infinite with a 360deg rotation keyframe.

FAQ

Animation vs transition — when to use which?

Use a transition for state changes between two values (hover, class toggle). Use an animation when you need multiple waypoints, looping, or a sequence the user did not trigger.

Why does my animation snap back at the end?

The default animation-fill-mode is none, so the element returns to its pre-animation styles when the animation completes. Use forwards to hold the end state.

Will animations run smoothly on every property?

Only transform and opacity are GPU-accelerated and avoid layout. Animating width, top, left, or margin causes reflow on every frame and stutters on lower-end devices.

How do I respect users who prefer reduced motion?

Wrap your animation rules in @media (prefers-reduced-motion: no-preference) so users with the OS setting enabled get no motion.

Try CSS Animation Builder