Nesting

CSS · Reference cheat sheet

📋 Overview

Native CSS nesting lets you write nested rules and at-rules like Sass, without a preprocessor. Use & for the parent selector. Keep nesting shallow for readability and specificity control.

🔧 Core concepts

• Nested style rule: a rule inside another; must usually start with & or a nesting selector when ambiguous.
• &: parent reference — .card \{ &:hover \{\} \} → .card:hover.
• Combinators: & > .child, & + &, & .desc.
• At-rules: nest @media, @supports, @layer, @container.
• Specificity: nested selectors concatenate — still counts as written.
• Declarations: may mix with nested rules; modern parsers allow declarations first or interleaved (browser-dependent historically — prefer declarations then nests).

.card {
  padding: 1rem;
  & h2 {
    margin: 0;
  }
  &:hover {
    box-shadow: 0 4px 12px rgb(0 0 0 / 0.1);
  }
  @media (min-width: 40rem) {
    padding: 1.5rem;
  }
}

💡 Examples

.nav {
  display: flex;
  & ul {
    display: flex;
    gap: 1rem;
    list-style: none;
  }
  & a {
    color: inherit;
    text-decoration: none;
    &:focus-visible {
      outline: 2px solid var(--accent);
    }
  }
}

/* BEM-ish without repetition */
.btn {
  border: 0;
  &--primary {
    background: var(--accent);
  }
  &__icon {
    margin-inline-end: 0.5rem;
  }
}

/* :is wrapping */
.prose {
  & :is(h1, h2, h3) {
    line-height: 1.2;
  }
}

/* Nested container */
.widget {
  container-type: inline-size;
  @container (min-width: 20rem) {
    & .meta {
      display: flex;
    }
  }
}

/* Invalid without & in some cases for starting type selectors — use & */
.card {
  & table {
  } /* good */
}

⚠️ Pitfalls

• Deep nesting (& & & &) recreates specificity hell — limit to 2–3 levels.
• Forgetting & can make selectors mean something else or be invalid.
• Output selector list can explode with :is — inspect DevTools.
• Mixing preprocessors + native nesting can double-process — pick one pipeline.
• Older browsers need PostCSS nesting plugin — know your baseline.

🔗 Related

• selectors.md — selector grammar
• specificity.md — weights
• media_queries.md — nested media
• container_queries.md — nested @container
• cascade_layers.md — @layer