npm ERR! ERESOLVE unable to resolve dependency tree
npm ERR! While resolving: my-app@1.0.0
npm ERR! Found: react@19.0.0
npm ERR! Could not resolve dependency:
npm ERR! peer react@"^18.0.0" from some-library@3.0.0

npm can’t figure out a set of package versions that satisfies all requirements. This is different from the peer dependency warning — ERESOLVE is a hard failure.

Fix 1: —legacy-peer-deps

npm install --legacy-peer-deps

This uses npm v6 behavior which is less strict about peer dependencies. Works 90% of the time.

Fix 2: —force

npm install --force

Forces installation, overriding conflicts. More aggressive than --legacy-peer-deps.

Fix 3: Update the Conflicting Package

# See which package is causing the conflict
npm ls react

# Update it
npm install some-library@latest

Often the latest version of the library supports your version of React/Node/etc.

Fix 4: Use overrides

Pin a specific version in package.json:

{
  "overrides": {
    "react": "19.0.0"
  }
}

Then rm -rf node_modules package-lock.json && npm install.

Make —legacy-peer-deps the Default

If you’re tired of adding the flag every time:

npm config set legacy-peer-deps true

Or add to .npmrc in your project root:

legacy-peer-deps=true

Related: npm Cheat Sheet · How Npm Install Actually Works