Svelte

The Svelte configuration has Svelte-specific configuration. This is a minimal preset as Biome doesn't yet have dedicated Svelte-specific linting rules, but it includes important overrides to prevent false positive linting errors in .svelte files.

Installation

Add the Svelte configuration to your biome.jsonc:

biome.jsonc

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

Overview

This configuration:

HTML Support: Enables experimental full HTML support with script and style indentation
React-Specific Props: Flags React-specific props like className and htmlFor since Svelte uses standard HTML attributes (class and for)
Svelte File Overrides: Relaxed rules for .svelte files to handle Svelte's component structure

HTML Formatter Configuration

The Svelte preset enables experimental HTML support with special formatting for embedded scripts and styles:

{
  "html": {
    "experimentalFullSupportEnabled": true,
    "formatter": {
      "indentScriptAndStyle": true
    }
  }
}

This configuration:

Experimental Full Support: Enables Biome's experimental HTML parsing and formatting capabilities for .svelte files
Indent Script and Style: Properly indents code inside <script> and <style> tags in Svelte components

Svelte-Specific Rules

Suspicious

Rule	Setting	Description
`noReactSpecificProps`	`error`	Disallow React-specific props like `className` and `htmlFor` in Svelte. Use `class` and `for` instead.

Svelte File Overrides

The following rules are disabled for .svelte files to prevent false positives due to Biome's partial support for Svelte components:

Correctness

Rule	Setting	Description
`noUnusedVariables`	`off`	Allow unused variables in `.svelte` files. Variables in the script section may only be used in the template.
`noUnusedImports`	`off`	Allow unused imports in `.svelte` files. Imports may only be used in the template section.

Style

Rule	Setting	Description
`useConst`	`off`	Allow `let` and `var` declarations in `.svelte` files for reactive statements.
`useImportType`	`off`	Disable explicit import type requirements for better compatibility with Svelte's build system.

Svelte

On this page