---
title: "Built-in utilities"
description: "Look up the CSS of a utility, or find the canonical utility for CSS declarations."
image: "https://stillwind.dev/og.png"
---

> Documentation Index
> Fetch the complete documentation index at: https://stillwind.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Built-in utilities

Type a utility to see its CSS, or type CSS declarations to find the utility that
produces them. Arbitrary values, such as `p-[16px]`, resolve to their canonical
spelling. The URL keeps your input, so you can share the results.

## Read the results

Each result shows one utility and its declarations. `&` stands for the styled
element. Comments show the resolved theme values and pixel sizes. A result for
CSS declarations names the declaration that it comes from.

The results leave out the theme variables and other supporting CSS that the full
stylesheet contains. The [macro reference](/docs/macros) shows complete
generated stylesheets.

A declaration without a matching utility becomes an arbitrary property, such as
`[hyphens:manual]`. Variants and shorthand properties can change what a utility
does, so compare its declarations with your CSS before you replace it.

## What the lookup covers

The lookup runs the Stillwind compiler in your browser with the default theme.
It downloads the compiler when the page opens. Utilities from your own `@theme`
tokens, such as `bg-brand`, do not resolve here. See
[Design systems](/docs/guides/design-systems) to add them, and hover over a
utility in the editor to check it in your project.

The editor and the CLI report non-canonical spellings with
[prefer-canonical-utilities](/docs/lints/prefer-canonical-utilities).

Source: https://stillwind.dev/docs/utilities/index.mdx