How to check unused npm packages?

This article is based on Node v16.15.1 and NPM 8.11.0.

When building an application it is very common to install various npm modules, the package.json and node-modules folder grow, so does the code for the application. It is best practice minimizing the code you have to maintain. A first step would be to remove unused code. Let's start with removing unused npm modules.

How to remove unused npm packages

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There are several solutions available, depcheck and npm-check are the most common ones.

depcheck

Depcheck analyzes the dependencies in a project to see: how each dependency is used, which dependencies are useless, and which dependencies are missing from package.json.

To use depcheck from the command line you have to install it. depcheck requires Node.js >= 10.

npm install -g depcheck

After installing it, it can be used with typing depcheck in the root project directory, where the package.json file is. The full syntax of the command looks like this depcheck [directory] [arguments]. Depending on the size of your project the execution can take a while.

Your output should look something like this.

I ran depcheck in the repository of this website. The output shows that I have six unused dependencies (3x dependencies, 3x dev dependencies), which I am going to remove with npm uninstall.

If you don't want to install depcheck globally, run it with npx.

npx depcheck

You can also pass additional arguments to depcheck, please have a look at the official documentation.

npm-check

npm-check checks for outdated, incorrect, and unused dependencies.

To use npm-check from the command line you have to install it. It requires Node >= 0.11.

npm install -g npm-check

After installing it, it can be used with typing npm-check in the root project directory, where the package.json file is. Depending on the size of your project the execution can take a while.

The output of npm-check has more information compared to depcheck.

I ran npm-check in the repository of this website, and the output is quite long, since I have not updated to the latest major version of gatsby (It's on the todo list.). npm-check will give you a nice and clear output of the out-of-date dependencies and unused dependencies. It also has a nice, interactive dependency update feature, when adding the -uor --update flag. npm-check will then show an interactive UI for choosing which modules to update and automatically updates versions referenced in the package.json. Have a look at the official documentation for a full list of options when using npm-check.

If you don't want to install npm-check globally, run it with npx.

npx npm-check

TL;DR

• Best practice is to remove unused code.
• Use tools like depcheck or npm-check to find unused dependencies.

Thanks for reading and if you have any questions, use the comment function or send me a message @mariokandut.

If you want to know more about Node, have a look at these Node Tutorials.

References (and Big thanks):

npm depcheck, Sameer, npm-check, fam