Configuration

One of Ultracite's best features is that it's zero-config out of the box – you can just extend the ultracite preset and get going. However, every project is a bit different, and you might want to customize certain rules or adapt Ultracite for different frameworks. This section explains the default configuration and how to extend or override it.

Ultracite provides framework-specific configurations that you can extend in addition to the base configuration. This allows you to add framework-specific linting rules without bloating the base config or dealing with irrelevant rules.

You can find the full list of available framework configurations in the Presets section.

Usage

To use a framework-specific configuration, add it to your extends array:

{
  "extends": ["ultracite/core", "ultracite/solid"]
}

You can combine multiple configurations if you're working on a multi-framework project or using something like Astro which supports multiple frameworks.

{
  "extends": ["ultracite/core", "ultracite/react", "ultracite/remix"]
}

Default configuration

When you include "extends": ["ultracite/core"] in your biome.jsonc, you are pulling in Ultracite's base preset configuration. This preset includes framework-agnostic rules and configurations. Some notable aspects of the default config:

• TypeScript strictness: Ultracite enables TypeScript's strict checks and lint rules requiring robust typing. For instance, it discourages use of any, requires handling of null/undefined, and prefers explicit types in certain situations to avoid ambiguity.
• ESLint "Recommended" equivalents: Common best-practice rules (no unused vars, no explicit eval, no proto pollution, etc.) are included.
• Accessibility: Rules equivalent to accessibility standards are on by default (ARIA attributes, semantic HTML, keyboard navigation, etc.).
• Node.js: Environment-specific quirks are handled. For example, global variables provided by Node (like module, process) are recognized so they won't be incorrectly flagged as undefined.
• Formatting conventions: Ultracite's formatter settings (largely inherited from Biome/Prettier defaults) include 2-space indentation, a max line width of 80 characters, semicolons at ends of statements, trailing commas where valid (e.g., in multi-line arrays/objects), single quotes for strings (except JSON, which uses double quotes), etc. These are chosen to match common conventions and ensure diff cleanliness.

All these defaults aim to enforce consistent style and prevent common errors without you having to manually configure each rule.

For a comprehensive reference of all linting rules configured in Ultracite's base configuration, see the Core Configuration documentation.

Overriding the configuration

Modifying biome.jsonc

You can disable rules by modifying the biome.jsonc file.

For example, to disable the noAutofocus rule, you can add the following:

{
  "linter": {
    "rules": {
      "a11y": {
        "noAutofocus": "off"
      }
    }
  }
}

Inline Comments

You can also disable rules on a per-line basis by adding a comment to the end of the line:

// biome-ignore lint/security/noDangerouslySetInnerHtml: This is a valid use case.
<div dangerouslySetInnerHTML={{ ... }} />