ESLint + Prettier Setup for Next.js 15

0.1.11 verified Sat Apr 25 auth: no javascript

eslint-prettier-next-15 (v0.1.11) is an automated CLI tool that configures ESLint (v9) and Prettier (v3) for Next.js 15 projects. It detects the package manager (npm, yarn, pnpm, or bun), removes old configurations, installs recommended dependencies (including @typescript-eslint, eslint-config-next, prettier plugins for import sorting and JSON formatting), and generates flat ESLint config and .prettierrc files. Designed for fresh or existing Next.js 15 apps, it enforces consistent code quality rules with zero manual setup. Updated irregularly; relies on flat config (eslint.config.mjs) and ESM-only imports.

Common errors

error Error [ERR_MODULE_NOT_FOUND]: Cannot find module 'next' ↓

cause The script is run in a directory that is not a Next.js project or lacks node_modules.

fix

Run the command in a Next.js 15 project root after installing dependencies.

error SyntaxError: Unexpected token 'export' (at eslint.config.mjs:1:1) ↓

cause Using an outdated Node.js version (<18) that does not support ES modules or top-level await.

fix

Upgrade Node.js to v18 or later, or ensure "type": "module" is in package.json.

error Error: Cannot find module '@eslint/eslintrc' ↓

cause Script dependencies were not fully installed due to network issue or failed npm install.

fix

Delete node_modules and package-lock.json, then run npm install again, or run the script again.

error eslint: 'import' is not defined (no-undef) ↓

cause The generated config does not include eslint-plugin-import, but the eslint:recommended rule may report this.

fix

Add 'eslint-plugin-import' to the plugins and extend 'plugin:import/errors' or disable the rule.

Warnings

breaking This script deletes existing ESLint and Prettier configuration files (.eslintrc.*, .prettierrc, .editorconfig, .vscode/settings.json) without backup. ↓

fix Manually backup your configuration files before running the script, or reapply them after setup.

deprecated The script installs eslint-config-next@15.1.4 which is pinned; it may become outdated as Next.js updates its ESLint config. ↓

fix After running the script, update eslint-config-next to the latest version manually: npm install eslint-config-next@latest --save-dev

gotcha Script expected to be run in a Next.js 15 project root. Running elsewhere will create config files in wrong directory. ↓

fix Ensure you are in the root directory of your Next.js 15 project before executing the command.

gotcha The generated eslint.config.mjs uses FlatCompat to extend 'next' and 'next/core-web-vitals'. This may not work if ESLint is not v9 or if next/core-web-vitals is not installed. ↓

fix Verify that eslint and eslint-config-next are installed and compatible.

Install

npm install eslint-prettier-next-15

yarn add eslint-prettier-next-15

pnpm add eslint-prettier-next-15

Imports

CLI usage

wrong

npm install -g eslint-prettier-next-15 && eslint-prettier-next-15

correct

npx eslint-prettier-next-15

The package is meant to be executed via npx, not installed globally.

eslint.config.mjs
wrong
```
.eslintrc.json or .eslintrc.js
```
correct
```
eslint.config.mjs (flat config file generated by script)
```
This tool generates the modern ESLint flat config format. Legacy .eslintrc files are not compatible with ESLint v9.
.prettierrc.json
wrong
```
prettier.config.js or .prettierrc.js
```
correct
```
.prettierrc.json (JSON with plugins array)
```
The generated config uses JSON format. Prettier also supports JS/TOML, but JSON is created here.

Quickstart

Creates a fresh Next.js 15 app, runs the setup script, then validates linting and formatting.

mkdir my-next-app && cd my-next-app
npx create-next-app@15 . --typescript --eslint=false --src-dir --app --import-alias '@/*' --no-tailwind
echo 'y' | npx eslint-prettier-next-15
npx eslint . --ext .ts,.tsx 2>/dev/null | head -5 || echo "No lint errors"
npx prettier --check "app/**/*.ts" 2>/dev/null | head -5 || echo "All files formatted"