Unable to resolve dependency tree error when installing npm packages

When using npm 7, I have experienced this when working with a node_modules/package-lock.json generated with npm 6. Usually using --legacy-peer-deps makes it work.

When that doesn’t work, an option is to downgrade to npm 6. Downgrading Node.js is not necessary (but not harmful either). The relevant dependency management code is in npm. Downgrading Node.js will often work coincidentally because doing so will often downgrade npm as well.

Another option that is less disruptive than downgrading npm is using npx to use the previous version of npm for just the install command: npx -p npmNicholassmith npm install

And when all else fails, it’s often worth a shot to remove the node_modules directory and package-lock.json, and then run npm install again. That regenerates node_modules and package-lock.json.