Pseudo-class Selectors

State selectors, structural selectors, and interactive states.

Overview

Pseudo-classes select elements based on state or position.

Key Concepts

• Hover/Active/Focus — Interactive states
• nth-child — Structural selection
• :has() — Parent selector
• :is() — Matches any selector
• :where() — Low specificity matching

Code Examples

/* Interactive states */
.button:hover {
  background: var(--primary-dark);
}

.button:active {
  transform: scale(0.98);
}

.input:focus {
  border-color: var(--primary);
  outline: none;
  box-shadow: 0 0 0 3px rgba(0, 123, 255, 0.25);
}

.input:focus-visible {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
}

/* :has() selector */
.form-group:has(:invalid) {
  border-color: red;
}

.form-group:has(:focus) {
  border-color: var(--primary);
}

.card:has(img) {
  display: grid;
  grid-template-columns: 200px 1fr;
}

/* Structural selectors */
.list-item:first-child {
  border-radius: 8px 8px 0 0;
}

.list-item:last-child {
  border-radius: 0 0 8px 8px;
}

.list-item:nth-child(odd) {
  background: #f9f9f9;
}

.list-item:nth-child(3n+1) {
  clear: both;
}

/* :is() and :where() */
:is(h1, h2, h3) {
  font-weight: bold;
  line-height: 1.2;
}

:where(.button, .link) {
  cursor: pointer;
  transition: all 0.2s ease;
}

/* State selectors */
.checkbox:checked + label {
  color: var(--primary);
}

.input:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.input:read-only {
  background: #f5f5f5;
}

/* Empty state */
.list:empty::before {
  content: 'No items found';
  color: #999;
}

/* Validation states */
.input:valid {
  border-color: green;
}

.input:invalid {
  border-color: red;
}

.input:placeholder-shown {
  opacity: 0.5;
}

/* Language selectors */
:lang(en) {
  font-family: serif;
}

:lang(ar) {
  direction: rtl;
}

/* Link states */
a:not([href]) {
  color: #999;
  pointer-events: none;
}

.visited-link:visited {
  color: purple;
}

Practice

Style a form using only pseudo-class selectors.