Configuration

Understand Ultracite's default presets, how framework-specific layers work, and which overrides to keep when your project needs custom rules.

One of Ultracite’s best features is that it’s zero-config out of the box — you can just extend the base preset and get going. However, every project is different, and you might want to customize certain rules or adapt Ultracite for different frameworks.

Framework Presets

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

The concept is the same across all supported linters — pull in the core preset, then layer on any framework presets you need — though the exact syntax differs per linter (Biome uses an extends array, while ESLint and Oxlint use imports; see the provider pages for each linter’s syntax). For example, if you’re using Biome with React and Next.js, you can pull in the following presets:

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

Default Configuration

When you include the core preset, you’re pulling in Ultracite’s base configuration. This preset includes framework-agnostic rules and settings. Some notable aspects:

• TypeScript strictness: Enables strict checks and lint rules requiring robust typing. Discourages use of any, requires handling of null/undefined, and prefers explicit types where needed.
• Best practices: Common rules like no unused vars, no explicit eval, no prototype pollution, etc.
• Accessibility: ARIA attributes, semantic HTML, keyboard navigation, and other a11y rules are enabled by default.
• Formatting conventions: 2-space indentation, 80-character line width, semicolons, trailing commas, and double quotes.

All these defaults aim to enforce consistent style and prevent common errors without manual configuration.

Type-Aware Rules

Ultracite ships an optional type-aware preset for Biome that enables project-graph rules — noPrivateImports, noUndeclaredDependencies, noUnresolvedImports, noImportCycles, and noDeprecatedImports. These rules require Biome’s scanner, so they’re slower and shipped as a separate layer:

{
  "extends": ["ultracite/biome/core", "ultracite/biome/type-aware"],
}

You can also enable this at setup time with npx ultracite init --type-aware. For Oxlint, the same flag installs oxlint-tsgolint for type-aware linting instead.

Safe Fixes

Most Ultracite rules only report errors — they don’t automatically modify your code. However, a few rules are configured with "fix": "safe", meaning they will auto-fix when you run ultracite fix. These fixes are non-breaking and safe to apply automatically:

If you want to disable auto-fixing for any of these, override the rule in your config and remove the fix property.

Overriding Rules

Each linter has its own way to disable or modify rules. For example, to disable the useButtonType rule for Biome, you can do the following:

{
  "extends": ["ultracite/biome/core"],
  "linter": {
    "rules": {
      "a11y": {
        "useButtonType": "off",
      },
    },
  },
}