While transitions animate between two states, @keyframes animations define a multi-step sequence that can run automatically, loop, and move through many intermediate states.
slide-in {
{ : (-); : ; }
{ : (); : ; }
}
{
: slide-in ease-out;
}
@keyframes bounce {
0% { transform: translateY(0); }
50% { transform: translateY(-30px); } /* peak of the bounce */
100% { transform: translateY(0); }
}
Percentages let you choreograph several stages in one animation — impossible with a simple transition.
.spinner {
animation: spin 1s linear infinite;
/* │ │ │ └── iteration-count (infinite = loop forever) */
/* │ │ └───────── timing function */
/* │ └────────────── duration */
/* └─────────────────── @keyframes name */
}
@keyframes spin { to { transform: rotate(360deg); } } /* classic loading spinner */
Other properties: animation-delay, animation-direction: alternate (ping-pong), animation-fill-mode: forwards (keep the final state), animation-play-state: paused.
/* ✅ GPU-composited, 60fps */
@keyframes good { to { transform: scale(1.1); opacity: 0.5; } }
/* ❌ animating width/height/top forces layout every frame → jank */
@keyframes bad { to { width: 300px; top: 50px; } }
Keyframe animations run on every frame, so animating layout-triggering properties is far more costly than animating transform/opacity.
@media (prefers-reduced-motion: reduce) {
.spinner { animation: none; } /* honor users sensitive to motion */
}
Keyframe animations power loaders, attention cues, entrances, and looping effects that transitions can't express (multi-step, auto-running, infinite).
Knowing the shorthand, sticking to transform/opacity for smoothness, and respecting prefers-reduced-motion lets you build rich motion that stays performant and accessible.
A library of IT interview questions with detailed answers — from Junior to Senior.
Donate