Ultracite Zero-config linting and formatting for JS/TS projects. Supports three linter backends: Biome (recommended), ESLint + Prettier, and Oxlint + Oxfmt. Detecting Ultracite Check if ultracite is in package.json devDependencies. Detect the active linter by looking for: biome.jsonc → Biome eslint.config.mjs → ESLint .oxlintrc.json → Oxlint CLI Commands

Check for issues (read-only)

bunx ultracite check

Auto-fix issues

bunx ultracite fix

Diagnose setup problems

bunx ultracite doctor

Initialize in a new project

bunx ultracite init

Replace

bunx

with

npx

,

pnpx

, or

yarn dlx

depending on the package manager.

check

and

fix

accept optional file paths:

bunx ultracite check src/index.ts

.

Initialization

bunx ultracite init

runs an interactive setup. For non-interactive (CI) use, pass flags:

bunx ultracite init

\

--pm

bun

\

--linter

biome

\

--editors

vscode cursor

\

--agents

claude copilot

\

--frameworks

react next

\

--integrations

husky lint-staged

\

--quiet

Flags:

--pm

—

npm

|

yarn

|

pnpm

|

bun

--linter

—

biome

(recommended) |

eslint

|

oxlint

--editors

—

vscode

|

zed

|

cursor

|

windsurf

|

antigravity

|

kiro

|

trae

|

void

--agents

—

claude

|

codex

|

copilot

|

cline

|

amp

|

gemini

|

cursor-cli

+ 19 more

--frameworks

—

react

|

next

|

solid

|

vue

|

svelte

|

qwik

|

remix

|

angular

|

astro

|

nestjs

--integrations

—

husky

|

lefthook

|

lint-staged

|

pre-commit

--hooks

— Enable auto-fix hooks for supported agents/editors

--type-aware

— Enable type-aware linting (oxlint only)

--skip-install

— Skip dependency installation

--quiet

— Suppress prompts (auto-detected when

CI=true

)

Init creates config that extends Ultracite presets:

// biome.jsonc

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

Framework presets available per linter:

core

,

react

,

next

,

solid

,

vue

,

svelte

,

qwik

,

remix

,

angular

,

astro

,

nestjs

.

Code Standards

When writing code in a project with Ultracite, follow these standards. For the full rules reference, see

references/code-standards.md

.

Key rules at a glance:

Formatting:

2-space indent, semicolons, double quotes, 80-char width, ES5 trailing commas, LF line endings.

Style:

Arrow functions preferred.

const

by default, never

var

.

for...of

over

.forEach()

. Template literals over concatenation. No enums (use objects with

as const

). No nested ternaries. Kebab-case filenames.

Correctness:

No unused imports/variables. No

any

(use

unknown

). Always

await

promises in async functions. No

console.log

/

debugger

/

alert

in production.

React:

Function components only. Hooks at top level. Exhaustive deps.

key

on iterables (no array index). No nested component definitions. Semantic HTML + ARIA.

Performance:

No accumulating spread in loops. No barrel files. No namespace imports. Top-level regex.

Security:

rel="noopener"

on

target="_blank"

. No

dangerouslySetInnerHTML

. No

eval()

.

Troubleshooting

Run

bunx ultracite doctor

to diagnose. It checks:

Linter installation (biome/eslint/oxlint binary available)

Config validity (extends ultracite presets correctly)

Ultracite in package.json dependencies

Conflicting tools (old

.eslintrc.*

,

.prettierrc.*

files)

Common fixes:

Conflicting configs

Delete legacy

.eslintrc.*

and

.prettierrc.*

files after migrating to Ultracite

Missing dependency

Run

bunx ultracite init

again or manually add

ultracite

to devDependencies

Rules not applying

Ensure config file extends the correct presets for your framework