word-break

word-break changes text line-breaking rules. It affects multiline text, not just a single-line fragment. Normal uses language-specific breaking; aggressive breaking can split ordinary words even when moving the whole word to the next line would work.

Compare break-all with emergency wrapping

The sentence contains ordinary words followed by a long token. Break-all can split ordinary words at the line edge; overflow-wrap:anywhere generally keeps a word intact when it can fit on the next line.

<p class="sample aggressive">
  Practice layout registrationidentifierwithoutspaces
</p>
<p class="sample emergency">
  Practice layout registrationidentifierwithoutspaces
</p>

.sample {
  max-width: 14ch;
  padding: 0.5rem;
  margin-block: 0.5rem;
  background: #eff6ff;
}
.aggressive {
  word-break: break-all;
}
.emergency {
  overflow-wrap: anywhere;
}

Compare CJK text with and without keep-all

Keep-all suppresses ordinary breaks within Chinese/Japanese/Korean text; it does not prohibit all spaces or punctuation breaks. Here overflow:auto keeps an intentionally unbroken line reachable.

<p class="sample" lang="zh">学习网页布局并检查文本换行。</p>
<p
  class="sample kept"
  lang="zh"
  tabindex="0"
  role="region"
  aria-label="Chinese text with keep-all"
>
  学习网页布局并检查文本换行。
</p>

.sample {
  max-width: 8rem;
  overflow: auto;
  padding: 0.5rem;
  margin-block: 0.5rem;
  background: #eff6ff;
}
.kept {
  word-break: keep-all;
}

Values and defaults

The initial value is normal and the property is inherited. Break-all permits additional breaks in non-CJK text. Keep-all suppresses ordinary CJK character breaks while leaving non-CJK normal behavior intact. The deprecated break-word value behaves like normal plus overflow-wrap:anywhere, regardless of the separately declared overflow-wrap value; it is not the same as overflow-wrap:break-word.

Auto-phrase performs language-aware phrase analysis where supported and needs a value-specific support check. Manual is specified but is not an interoperable implemented value.

Choose a language-aware rule

Do not apply break-all to all prose to mask a sizing bug. Use overflow-wrap for long-token emergencies and hyphens for dictionary/manual hyphenation. Language metadata helps the browser choose text-processing rules.

Learn white-space and html language. Test real content in each supported language.

Sources and browser support

MDN: word-break describes the syntax and links to the specification and compatibility data. Check individual values in that table when supporting older browsers.