/* Keyword values */
break-inside: auto;
break-inside: avoid;
break-inside: avoid-page;
break-inside: avoid-column;
break-inside: avoid-region;

/* Global values */
break-inside: inherit;
break-inside: initial;
break-inside: revert;
break-inside: revert-layer;
break-inside: unset;

Each possible break point (in other words, each element boundary) is affected by three properties: the break-after value of the previous element, the break-before value of the next element, and the break-inside value of the containing element.

To determine if a break must be done, the following rules are applied:

1. If any of the three concerned values is a forced break value (always, left, right, page, column, or region), it has precedence. If more than one of them are such a break, the value of the element that appears the latest in the flow is used. Thus, the break-before value has precedence over the break-after value, which in turn has precedence over the break-inside value.
2. If any of the three concerned values is an avoid break value (avoid, avoid-page, avoid-region, or avoid-column), no such break will be applied at that point.

Once forced breaks have been applied, soft breaks may be added if needed, but not on element boundaries that resolve in a corresponding avoid value.

auto

Allows, but does not force, any break (page, column, or region) to be inserted within the principal box.

avoid

Avoids any break (page, column, or region) from being inserted within the principal box.

avoid-page

Avoids any page break within the principal box.

avoid-column

Avoids any column break within the principal box.

avoid-region

Avoids any region break within the principal box.

For compatibility reasons, the legacy page-break-inside property should be treated by browsers as an alias of break-inside. This ensures that sites using page-break-inside continue to work as designed. A subset of values should be aliased as follows:

break-inside = 
  auto          |
  avoid         |
  avoid-page    |
  avoid-column  |
  avoid-region  

In the following example we have a container that contains an <h1> spanning all columns (achieved using column-span: all) and a series of paragraphs laid out in multiple columns using column-width: 200px. We also have a <figure> containing an image and a caption.

By default, it is possible for you to get a break between the image and its caption, which is not what we want. To avoid this, we have set break-inside: avoid on the <figure>, which causes them to always stay together.

HTML

<article>
  <h1>Main heading</h1>

  <p>
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nulla vitae
    fringilla mauris. Quisque commodo eget nisi sed pretium. Mauris luctus nec
    lacus in ultricies. Mauris vitae hendrerit arcu, ac scelerisque lacus.
    Aliquam lobortis in lacus sit amet posuere. Fusce iaculis urna id neque
    dapibus, eu lacinia lectus dictum.
  </p>

  <figure>
    <img
      src="https://images.weserv.nl/?url=https%3A%2F%2Fmdn.dev%2Farchives%2Fmedia%2Fattachments%2F2020%2F07%2F29%2F17350%2F3b4892b7e820122ac6dd7678891d4507%2Ffirefox.png&q=12&output=webp&max-age=110" />
    <figcaption>The Firefox logo — fox wrapped around the world</figcaption>
  </figure>

  <p>
    Praesent condimentum dui dui, sit amet rutrum diam tincidunt eu. Cras
    suscipit porta leo sit amet rutrum. Sed vehicula ornare tincidunt. Curabitur
    a ipsum ac diam mattis volutpat ac ut elit. Nullam luctus justo non
    vestibulum gravida. Morbi metus libero, pharetra non porttitor a, molestie
    nec nisi.
  </p>

  <p>
    In finibus viverra enim vel suscipit. Quisque consequat velit eu orci
    malesuada, ut interdum tortor molestie. Proin sed pellentesque augue. Nam
    risus justo, faucibus non porta a, congue vel massa. Cras luctus lacus nisl,
    sed tincidunt velit pharetra ac. Duis suscipit faucibus dui sed ultricies.
  </p>
</article>

CSS

html {
  font-family: helvetica, arial, sans-serif;
}

body {
  width: 80%;
  margin: 0 auto;
}

h1 {
  font-size: 3rem;
  letter-spacing: 2px;
  column-span: all;
}

h1 + p {
  margin-top: 0;
}

p {
  line-height: 1.5;
  break-after: column;
}

figure {
  break-inside: avoid;
}

img {
  max-width: 70%;
  display: block;
  margin: 0 auto;
}

figcaption {
  font-style: italic;
  font-size: 0.8rem;
  width: 70%;
}

article {
  column-width: 200px;
  gap: 20px;
}

• Learn: Multiple-column Layout
• Breaking Boxes With CSS Fragmentation