`rule-inset-cap` CSS property

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The rule-inset-cap CSS shorthand property can be used to offset the column and row rule segment cap endpoints to the same value.

Try it

rule-inset-cap: -20px;

rule-inset-cap: 0;

rule-inset-cap: 1em;

rule-inset-cap: 100%;

rule-inset-cap: overlap-join;

<section id="default-example">
  <div id="example-element">
    <i>A</i>
    <i>B</i>
    <i>C</i>
    <i>D</i>
    <i>E</i>
    <i>F</i>
    <i>G</i>
    <i>H</i>
    <i>I</i>
    <i>J</i>
    <i>K</i>
    <i>L</i>
    <i>M</i>
    <i>N</i>
    <i>O</i>
    <i>P</i>
    <i>Q</i>

    <i id="y">Y</i>
    <i id="z">Z</i>
    <i id="bang">!</i>
  </div>
</section>

#example-element {
  display: grid;
  grid-template-columns: repeat(7, 1fr);
  rule: solid thick magenta;
  column-rule-color: rebeccapurple;
  gap: 1em;
  rule-overlap: column-over-row;
  rule-visibility-items: between;
  border: 1px solid rebeccapurple;
  overflow: visible;
  margin: 1em;
}
#example-element i {
  padding: 8px;
  border: 1px dashed;
}
#y {
  grid-column: 4 / 5;
  grid-row: 4 / 5;
}
#z {
  grid-column: 5 / 6;
  grid-row: 4 / 5;
}
#bang {
  grid-column: 6 / 7;
  grid-row: 4 / 5;
}

Constituent properties

This property is a shorthand for the following CSS properties:

Syntax

css

/* Keywords */
rule-inset-cap: overlap-join;

/* A <length-percentage> value */
rule-inset-cap: 0;
rule-inset-cap: 1em;
rule-inset-cap: -5px;
rule-inset-cap: -25%;

/* Two values */
rule-inset-cap: 0 20px;
rule-inset-cap: 1em -5px;
rule-inset-cap: overlap-join -25%;

/* Global values */
rule-inset-cap: inherit;
rule-inset-cap: initial;
rule-inset-cap: revert;
rule-inset-cap: revert-layer;
rule-inset-cap: unset;

Values

This property is specified as one or two values from the following list:

overlap-join: Resolves to 0.
<length-percentage>: Specifies the size of the inset. Percentage values resolve to 0 for caps at the container's edge. For interior gaps, percentages are relative to the height of the adjacent row-gap for column segment caps, or the width of the adjacent column-gap for row segment caps.

The rule-inset-cap shorthand property can be used to set the row-rule-inset-cap and column-rule-inset-cap properties to the same value in a single declaration, insetting row and column cap segment endpoints by the specified values.

If you specify one value, both the start and end cap segment endpoints are set to that value. If you specify two values, the row and column cap start segment endpoints are set to the first value, and the row and column cap end segment endpoints are set to the second value.

The default value is 0, which, in the case of cap endpoints, is the same as overlap-join. Positive values reduce the segment size, while negative values increase it.

The rule-inset-cap property, along with the rule-inset-junction property, can be set using the rule-inset shorthand.

Formal definition

Value not found in DB!

Formal syntax

rule-inset-cap = 
  <'column-rule-inset-cap'>  

<column-rule-inset-cap> = 
  <inset-value> <inset-value>?  

<inset-value> = 
  <length-percentage>  |
  overlap-join         

<length-percentage> = 
  <length>      |
  <percentage>

Examples

Basic usage

This example shows how to set rule-inset-cap to inset the endpoints of cap segments on flex containers.

HTML

html

<h1>Insetting cap endpoints</h1>
<article>
  <section>
    <h2>flex-direction: row</h2>
    <div class="flexbox">
      <div></div>
      <div></div>
      <div></div>
      <div></div>
      <div></div>
      <div></div>
      <div></div>
    </div>
  </section>
  <section>
    <h2>flex-direction: column</h2>
    <div class="flexbox column">
      <div></div>
      <div></div>
      <div></div>
      <div></div>
      <div></div>
      <div></div>
      <div></div>
    </div>
  </section>
</article>

<p>
  <label
    >Change the size of the inset.
    <input type="range" min="-40" max="16" value="16" id="inset"
  /></label>
  <output id="o">16px</output>
</p>

CSS

We use the display property to turn the .flexbox elements into flex containers. We balance the items into three flex lines using flex-wrap and flex-line-count. We define a light blue rule to paint in both row and column gaps, then override the column-rule-color, setting darker blue vertical gap decorations. Finally, we set the rule-inset-cap to 16px.

css

.flexbox {
  display: flex;
  flex-wrap: balance;
  flex-line-count: 3;
  gap: 20px;
  rule: 5px solid lightblue;
  column-rule-color: blue;

  rule-inset-cap: 16px;
}

We also set the flex-direction on the .column container to make its items flow in columns rather than rows. We've hidden the other CSS styles, and the code that make the form interactive, for brevity.

css

.column {
  flex-direction: column;
}

h1,
article {
  font-family: sans-serif;
  text-align: center;
}
h1 {
  font-size: 1.25em;
}
h2 {
  font-size: 1em;
}
article {
  display: flex;
  gap: 5vw;
  rule: 1px solid black;
  width: 90vw;
  margin: auto;
}
section {
  flex-basis: 45vw;
}
.flexbox > div {
  border: 1px solid green;
  background-color: lime;
  flex: 1 1 auto;
  height: 30px;
}
output {
  display: inline-block;
  width: 2em;
}
p {
  margin-top: 2.5em;
}
@layer no-support {
  @supports not (rule-inset-cap: 16px) {
    body::before {
      content: "Your browser doesn't support the rule-inset-cap property";
      background-color: wheat;
      display: block;
      text-align: center;
      padding: 1rem 0;
    }
  }
}

const inset = document.getElementById("inset");
const containers = document.querySelectorAll(".flexbox");
const output = document.getElementById("o");

inset.addEventListener("input", () => {
  const val = `${inset.value}px`;
  containers[0].style.ruleInsetCap = val;
  containers[1].style.ruleInsetCap = val;
  output.innerText = val;
});

Result

Change the size of the inset.

Setting two values

HTML

<p>
  <label
    >Change the <code>row-rule-inset-cap</code> value.
    <input type="range" min="-40" max="40" value="40" id="row" data-unit="px"
  /></label>
  <output id="og">40px</output>
</p>
<p>
  <label
    >Change the <code>column-rule-inset-cap</code> value.
    <input type="range" min="-40" max="40" value="-40" id="col" data-unit="px"
  /></label>
  <output id="ow">-40px</output>
</p>

Our HTML includes an unordered list (<ul>) with nine list items (<li>):

html

<ul>
  <li>1</li>
  <li>2</li>
  <li>3</li>
  <li>4</li>
  <li>5</li>
  <li>6</li>
  <li>7</li>
  <li>8</li>
  <li>9</li>
</ul>

The user interface for selecting different values and the JavaScript that enables the interactivity have been hidden for brevity.

CSS

We create a grid container by setting the display to grid, creating 4 columns with grid-template-columns, and adding a 30px gap. We use the row-rule and column-rule properties to define our rules. We then use the rule-inset-cap property to inset the start cap segment endpoints by 40px and outset the end cap segment endpoints by -40px.

We also set the 6th grid item to span two columns.

css

ul {
  display: grid;
  grid-template-columns: repeat(4, auto);
  gap: 30px;
  row-rule: 16px solid olive;
  column-rule: 10px solid palegoldenrod;

  rule-inset-cap: 40px -40px;
}
li:nth-of-type(6) {
  grid-column-end: span 2;
}

ul {
  width: calc(95vw - 80px);
  border: 1px solid;
  list-style-type: none;
  margin: auto;
  padding: 0;
  place-items: center;
}
li {
  place-content: center;
  text-align: center;
  font-family: sans-serif;
  background-color: #ededed;
  padding: 5vw;
  width: 100%;
  box-sizing: border-box;
}
li:nth-of-type(6) {
  padding: 2em 0;
}
li code {
  display: block;
  margin: 0 auto;
  text-align: left;
  background-color: #fcfcfc;
  width: calc(47.5vw - 40px);
}
output {
  font-family: monospace;
}
input {
  accent-color: olive;
}
@layer no-support {
  @supports not (rule-inset-cap: 16px) {
    body::before {
      content: "Your browser doesn't support the rule-inset-cap property";
      background-color: wheat;
      display: block;
      text-align: center;
      padding: 1rem 0;
    }
  }
}

const ul = document.querySelector("ul");
const rowSize = document.getElementById("row");
const og = document.getElementById("og");
const colSize = document.getElementById("col");
const ow = document.getElementById("ow");
const cell = document.querySelector("li:nth-of-type(6)");
let text = "";
const update = function () {
  ul.style.ruleInsetCap = text = `${rowSize.value}px ${colSize.value}px`;
  cell.innerHTML = `<code>rule-inset-cap: ${text};</code>`;
};

update();

rowSize.addEventListener("input", () => {
  og.innerText = `${rowSize.value}px`;
  update();
});

colSize.addEventListener("input", () => {
  ow.innerText = `${colSize.value}px`;
  update();
});

Result

Change the inset values for the starts and ends of the cap segment endpoints.

Inner cap segments

This example shows how to set rule-inset-cap to inset the endpoints of cap segments on a grid container, and how the rule-visibility-items property can turn inner endpoints into cap segment endpoints.

HTML

We include an unordered list (<ul>) as our container for several list items (<li>).

We also include a <select> element with an <option> for each rule-visibility-items keyword, and an <input> of type range.

html

<ul id="ul">
  <li>1</li>
  <li>2</li>
  <li>3</li>
  <li>4</li>
  <li>5</li>
  <li>6</li>
  <li>7</li>
  <li>8</li>
  <li>9</li>
  <li>10</li>
  <li>11</li>
  <li>12</li>
  <li>13</li>
  <li>14</li>
  <li>15</li>
  <li>16</li>
  <li>17</li>
</ul>

<p>
  <label
    ><code>rule-visibility-items</code> value <code>
    <select id="visibility">
      <option>all</option>
      <option>between</option>
      <option>around</option>
      <option selected>normal</option>
  </select>
  </label>
</p>

<p>
  <label
    >Change the inset size.
    <input type="range" min="-40" max="16" value="0" id="inset" data-unit="px"
  /></label>
  <output id="o"></output>
</p>

CSS

We create a grid container by setting the display to grid, creating 6 columns with grid-template-columns, and adding a 20px gap. We use the rule property to define our rules, overriding the row rule color with the row-rule-color property. We set the rule-break property to break the rules at each intersection, making each rule segment distinct. We explicitly set rule-visibility-items to the default value of normal. We then use the rule-inset-cap property to inset all the cap segment endpoints by 16px.

We also set the seventh list item to span two columns using the grid-column-end property.

css

ul {
  display: grid;
  grid-template-columns: repeat(6, auto);
  gap: 20px;
  rule: 10px solid olive;
  row-rule-color: palegoldenrod;
  rule-break: intersection;
  rule-visibility-items: normal;

  rule-inset-cap: 16px;
}

li:nth-of-type(7) {
  grid-column-end: span 2;
}

We've hidden the other CSS styles, and the code that make the form interactive, for brevity.

ul {
  place-items: center;
  padding: 0;
  list-style-type: none;
  border: 1px solid;
  margin: 40px;
}
li {
  text-align: center;
  font-family: sans-serif;
  background-color: #ededed;
  padding: 1em;
  width: 100%;
  box-sizing: border-box;
}
li:nth-of-type(n + 9) {
  grid-row: 3 / 4;
}
li:nth-of-type(n + 12) {
  grid-row: 4 / 5;
}
li:nth-of-type(10) {
  grid-column: 5/6;
}
li:nth-of-type(11) {
  grid-column: 6/7;
}

li:nth-of-type(15) {
  grid-area: 4 / 5 / 5 / 6;
}
li:nth-of-type(16) {
  grid-area: 4 / 6 / 5 / 7;
}
li:nth-of-type(17) {
  display: none;
  grid-area: 5 / 6 / 6 / 7;
}
@layer no-support {
  @supports not (rule-inset-cap: 16px) {
    body::before {
      content: "Your browser doesn't support the rule-inset-cap property";
      background-color: wheat;
      display: block;
      text-align: center;
      padding: 1rem 0;
    }
  }
}

const inset = document.getElementById("inset");
const visibility = document.getElementById("visibility");
const ul = document.getElementById("ul");
const output = document.getElementById("o");

inset.addEventListener("input", () => {
  output.innerText =
    ul.style.ruleInsetCap = `${inset.value}${inset.dataset["unit"]}`;
});

visibility.addEventListener("change", () => {
  ul.style.ruleVisibilityItems = `${visibility.value}`;
});

Result

Select between from the dropdown to paint only rule segments when both adjacent grid areas contain a grid item, thereby creating interior cap segments. Now change the inset value to visualize which segment endpoints are cap segment endpoints.

Specifications

Specification
CSS Gaps Module Level 1 # propdef-rule-inset-cap

Browser compatibility

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`rule-inset-cap` CSS property

Try it

Constituent properties

Syntax

Values

Description

Formal definition

Formal syntax

Examples

Basic usage

HTML

CSS

Result

Setting two values

HTML

CSS

Result

Inner cap segments

HTML

CSS

Result

Specifications

Browser compatibility

See also

Help improve MDN

rule-inset-cap CSS property

HTML

CSS

Result

HTML

CSS

Result

HTML

CSS

Result

Help improve MDN

`rule-inset-cap` CSS property