npm WARN ... requires a peer of ... but none is installed. You must install peer dependencies yourself

Question

"A requires a peer of B but none was installed". Consider it as "A requires one of B's peers but that peer was not installed and we're not telling you which of B's peers you need."

The automatic installation of peer dependencies was explicitly removed with npm 3.

NPM Blog

Release notes of v3

So you cannot install peer dependencies automatically with npm 3 and upwards.

Updated Solution:

Use following for each peer dependency to install that and remove the error

npm install --save-dev xxxxx

Deprecated Solution:

1. You can use npm-install-peers to find and install required peer dependencies.

   npm install -g npm-install-peers

   npm-install-peers

2. If you are getting this error after updating any package's version then remove node_modules directory and reinstall packages by npm install or npm cache clean and npm install.

For each error of the form:

npm WARN {something} requires a peer of {other thing} but none is installed. You must install peer dependencies yourself.

You should:

$ npm install --save-dev "{other thing}"

Note: The quotes are needed if the {other thing} has spaces, like in this example:

npm WARN [email protected] requires a peer of rollup@>=0.66.0 <2 but none was installed.

Resolved with:

$ npm install --save-dev "rollup@>=0.66.0 <2"

The accepted answer of using npm-install-peers did not work, nor removing node_modules and rebuilding. The answer to run

npm install --save-dev @xxxxx/xxxxx@latest

for each one, with the xxxxx referring to the exact text in the peer warning, worked. I only had four warnings, if I had a dozen or more as in the question, it might be a good idea to script the commands.

I had a similar issue and solved after running these instructions!

npm install npm -g
npm install --save-dev @angular/cli@latest
npm install
npm start