framer-motion

// Shared layout - the element "slides" between two positions
<motion.div layoutId="highlight" className={activeTab === id ? "active" : ""} />
 
// Auto layout - animates position/size when layout changes
<motion.div layout>
  {isExpanded && <motion.p layout>Additional content</motion.p>}
</motion.div>
 
// layout="position" - animates position only (not size)
// layout="size" - animates size only
// layout="preserve-aspect" - preserves the ratio during the transition

import { stagger } from "motion/react";
 
const container = {
  hidden: { opacity: 0 },
  show: {
    opacity: 1,
    transition: {
      // staggerChildren + staggerDirection are DEPRECATED (Motion 12.22, Jul 2025).
      // Pass a stagger() function to delayChildren instead.
      delayChildren: stagger(0.08, { startDelay: 0.2 }),
      // reverse order: stagger(0.08, { from: "last" })
      // also available: from: "first" | "center" | "last" | index, and ease
    },
  },
};
 
const item = {
  hidden: { opacity: 0, y: 20 },
  show: { opacity: 1, y: 0 },
};
 
<motion.ul variants={container} initial="hidden" animate="show">
  {items.map((i) => (
    <motion.li key={i.id} variants={item} />
  ))}
</motion.ul>

<motion.div
  whileHover={{ scale: 1.05 }}
  whileTap={{ scale: 0.95 }}
  whileFocus={{ borderColor: "#3b82f6" }}
  // Drag
  drag               // true = x+y, "x" = horizontal only, "y" = vertical only
  dragConstraints={{ left: -100, right: 100, top: -50, bottom: 50 }}
  dragElastic={0.2}  // 0 = rigid, 1 = free (default 0.35)
  dragSnapToOrigin   // returns to initial position
  onDragEnd={(e, info) => {
    if (info.offset.x > 100) handleSwipe("right");
  }}
/>

const x = useMotionValue(0);
const opacity = useTransform(x, [-200, 0, 200], [0, 1, 0]);
const background = useTransform(x, [-200, 200], ["#ff0000", "#00ff00"]);
 
// Spring-based smoothing
const smoothX = useSpring(x, { stiffness: 300, damping: 30 });
 
// Scroll tracking
const { scrollY, scrollYProgress } = useScroll();
const parallaxY = useTransform(scrollYProgress, [0, 1], [0, -300]);
 
// Element-scoped scroll
const ref = useRef(null);
const { scrollYProgress } = useScroll({
  target: ref,
  offset: ["start end", "end start"],
});

import isPropValid from "@emotion/is-prop-valid";
import { MotionConfig } from "motion/react";
 
<MotionConfig isValidProp={isPropValid}>
  <App />
</MotionConfig>

// BAD - infinite re-render if animate depends on state
onUpdate={(latest) => setPosition(latest.x)}
 
// GOOD - guard or useMotionValueEvent
const x = useMotionValue(0);
useMotionValueEvent(x, "change", (latest) => {
  if (latest > threshold) onThresholdReached();
});

// BAD - key changes every render, breaks layout tracking
<motion.div layout key={Math.random()} />
 
// GOOD - stable key derived from data
<motion.div layout key={item.id} />

// BAD - no key, exit animation does not trigger
<AnimatePresence>
  {isOpen && <motion.div exit={{ opacity: 0 }} />}
</AnimatePresence>
 
// GOOD - unique key for each conditional child
<AnimatePresence>
  {isOpen && <motion.div key="modal" exit={{ opacity: 0 }} />}
</AnimatePresence>

// BAD - double animation, transform conflicts
<motion.div animate={{ x: 100 }}>
  <motion.div animate={{ x: -50 }}>Content</motion.div>
</motion.div>
 
// GOOD - single animation level per transform axis
<motion.div animate={{ x: 100 }}>
  <motion.div animate={{ opacity: 0.5 }}>Content</motion.div>
</motion.div>
 
// GOOD - use variants to coordinate parent/child
<motion.div variants={parent} animate="active">
  <motion.div variants={child} />
</motion.div>