:nth-of-type

The :nth-of-type selector allows you select one or more elements based on their source order, according to a formula. It is defined in the CSS Selectors Level 3 spec as a “structural pseudo-class”, meaning it is used to style content based on its relationship with parent and sibling elements.

Suppose we have an unordered list and wish to “zebra-stripe” alternating list items:

<ul>
  <li>First Item</li>
  <li>Second Item</li>
  <li>Third Item</li>
  <li>Fourth Item</li>
  <li>Fifth Item</li>
</ul>

Rather than adding classes to each list item (eg .even & .odd) we can use :nth-of-type:

li {
  background: slategrey;
}
/* select alternating items starting with the second item */
li:nth-of-type(2n) {
  background: lightslategrey;
}

As you can see, :nth-of-type takes an argument: this can be a single integer, the keywords “even” or “odd”, or a formula as shown above. If an integer is specified only one element is selected—but the keywords or a formula will iterate through all the children of the parent element and select matching elements—similar to navigating items in an array in JavaScript. Keywords “even” and “odd” are straightforward, but the formula is constructed using the syntax an+b, where:

• “a” is an integer value
• “n” is the literal letter “n”
• “+” is an operator and may be either “+” or “-”
• “b” is an integer and is required if an operator is included in the formula

It is important to note that this formula is an equation, and iterates through each sibling element, determining which will be selected. The “n” part of the formula, if included, represents a set of increasing positive integers (just like iterating through an array). In our above example, we selected every second element with the formula 2n, which worked because every time an element was checked, “n” increased by one (2×0, 2×1, 2×2, 2×3, etc). If an element’s order matches the result of the equation, it gets selected (2, 4, 6, etc). For a more in-depth explanation of the math involved, please read this article.

To illustrate further, here are some examples of valid :nth-of-type selectors:

Luckily, you don’t always have to do the math yourself—there are several :nth-of-type testers and generators out there:

• CSS-Tricks Tester
• Lea Verou’s Tester

Points of Interest

• :nth-of-type iterates through elements starting from the top of the source order. The only difference between it and :nth-last-of-type is that the latter iterates through elements starting from the bottom of the source order.
• The :nth-of-type selector is very similar to :nth-child but with one critical difference: it is more specific. In our example above they would produce the same result because we are iterating over only li elements, but if we were iterating over a more complex group of siblings, :nth-child would try to match all siblings, not only siblings of the same element type. This reveals the power of :nth-of-type—it targets a particular type of element in an arrangement with relation to similar siblings, not all siblings.

Related Properties

• nth-last-of-type
• nth-child
• nth-last-child
• first-of-type
• last-of-type

Other Resources

• Mozilla Docs
• QuirksMode article
• Sitepoint article

Browser Support

Data on support for the mdn-css__selectors__nth-of-type feature across the major browsers

:nth-of-type was introduced in CSS Selectors Module 3, which means old versions of browsers do not support it. However, modern browser support is impeccable, and the new pseudo-selectors are widely used in production environments. If you require older browser support, either polyfill for IE, or use these selectors in non-critical ways á la progressive enhancement, which is recommended.