npm ERR! code ERESOLVE / ERESOLVE unable to resolve dependency tree / Could not resolve dependency: peer react@... — how do I fix it properly?

Cause: since npm 7, npm installs peer dependencies automatically and refuses to install when two packages need incompatible versions of the same peer. A typical case is a library that declares peerDependencies react ^17 while your app uses react 18 or 19. npm 6 only warned about this, so older projects and tutorials often hit ERESOLVE after upgrading Node/npm. How to check: - Read the error: the 'Found:' line is what you have, and the 'Could not resolve dependency: peer X' line names the package that wants a different version. - npm ls <peer-package> and npm view <conflicting-package> peerDependencies show what each side requires. Fix (best first): 1. Upgrade the package that declares the outdated peer range to a release that supports your version (npm view <pkg> versions, check its changelog), or replace it if it's abandoned. 2. If you're sure the combination works, override the version in package.json with "overrides" (npm 8.3+), which pins the dependency for the whole tree and is recorded in the lockfile. 3. As a temporary workaround, install with --legacy-peer-deps (npm 6 behavior: peers are not auto-installed or checked). Put legacy-peer-deps=true in the project's .npmrc if you need it, so CI and teammates behave the same way. Avoid --force, which accepts conflicting versions and can leave broken installs. 4. Don't delete package-lock.json as a fix; it hides the conflict and changes many unrelated versions. After: run your tests and the app, commit the lockfile and any .npmrc change, and remove the workaround once the dependency catches up. Sources: https://docs.npmjs.com/cli/v11/using-npm/config#legacy-peer-deps https://docs.npmjs.com/cli/v11/configuring-npm/package-json#overrides https://blog.openreplay.com/fix-npm-err-eresolve-dependency