eslint version conflict with TypeScript — how to fix

Q: Align the config format with the ESLint major version

ESLint 9 projects normally use eslint.config.js , while older projects may still use .eslintrc . Do not upgrade only ESLint while leaving the parser and plugin on an incompatible major version. ``` # Check peer requirements before installing npm view @typescript-eslint/parser peerDependencies npm view @typescript-eslint/eslint-plugin peerDependencies # Reinstall a matching set after choosing ESLint 8 or 9 npm install --save-dev eslint@ @typescript-eslint/parser@ @typescript-eslint/eslint-plugin@ ```

Quick Answer

# ESLint 9 (flat config) — use latest @typescript-eslint
npm install --save-dev eslint@^9 @typescript-eslint/parser@^8 @typescript-eslint/eslint-plugin@^8

# ESLint 8 (legacy config) — use v6
npm install --save-dev eslint@^8 @typescript-eslint/parser@^6 @typescript-eslint/eslint-plugin@^6

When this happens

npm ERR! peer eslint@"^8.56.0" from @typescript-eslint/[email protected]
npm ERR! node_modules/@typescript-eslint/eslint-plugin
npm ERR!   Conflicting peer dependency: [email protected]

ESLint and @typescript-eslint must be at compatible major versions.

Other causes & fixes

Check current installed versions

npm ls eslint @typescript-eslint/parser @typescript-eslint/eslint-plugin

ESLint 9 flat config — eslint.config.js

// eslint.config.js (ESLint 9)
import tseslint from 'typescript-eslint';

export default tseslint.config(
  ...tseslint.configs.recommended
);

ESLint 8 legacy config — .eslintrc.json

// .eslintrc.json (ESLint 8)
{
  "parser": "@typescript-eslint/parser",
  "plugins": ["@typescript-eslint"],
  "extends": ["plugin:@typescript-eslint/recommended"]
}

Find which package is requesting the conflicting version

The package named in the peer dependency error is not always the package you installed directly. Inspect the dependency tree before pinning a version.

npm ls eslint @typescript-eslint/parser @typescript-eslint/eslint-plugin
npm explain eslint
node --version
npm --version

Align the config format with the ESLint major version

ESLint 9 projects normally use eslint.config.js, while older projects may still use .eslintrc. Do not upgrade only ESLint while leaving the parser and plugin on an incompatible major version.

# Check peer requirements before installing
npm view @typescript-eslint/parser peerDependencies
npm view @typescript-eslint/eslint-plugin peerDependencies

# Reinstall a matching set after choosing ESLint 8 or 9
npm install --save-dev eslint@<major> @typescript-eslint/parser@<major> @typescript-eslint/eslint-plugin@<major>