This post goes over how to fix npm error ERESOLVE could not resolve.

Problem

If there’s an npm dependency conflict, npm install will throw an error:

npm install

npm error code ERESOLVE
npm error ERESOLVE could not resolve
npm error
npm error While resolving: [email protected]
npm error Found: [email protected]
npm error node_modules/firebase
npm error   firebase@"11.0.1" from the root project
npm error
npm error Could not resolve dependency:
npm error peer firebase@"^9.1.3 || ^10.0.0" from [email protected]
npm error node_modules/firebaseui
npm error   firebaseui@"6.1.0" from the root project
npm error
npm error Conflicting peer dependency: [email protected]
npm error node_modules/firebase
npm error   peer firebase@"^9.1.3 || ^10.0.0" from [email protected]
npm error   node_modules/firebaseui
npm error     firebaseui@"6.1.0" from the root project
npm error
npm error Fix the upstream dependency conflict, or retry
npm error this command with --force or --legacy-peer-deps
npm error to accept an incorrect (and potentially broken) dependency resolution.

Solution

A temporary workaround is to install with --force:

npm install --force

Or with --legacy-peer-deps:

npm install --legacy-peer-deps

However, a better solution is to use overrides:

{
  "overrides": {
    "your-dependency": "1.0.0"
  }
}

For example, firebaseui depends on a different version of firebase so to specify it in overrides:

{
  "dependencies": {
    "firebase": "11.0.1",
    "firebaseui": "6.1.0"
  },
  "overrides": {
    "firebase": "11.0.1"
  }
}

Alternatively, you can use the version from dependencies:

{
  "dependencies": {
    "firebase": "11.0.1",
    "firebaseui": "6.1.0"
  },
  "overrides": {
    "firebase": "$firebase"
  }
}