NPM (Node Package Manager) and Yarn are both JavaScript based package managers for ease of installing 3rd Party Tools & Libraries into your modern web development workflow. They revolutionized the way people shared code. Instead of having to tediously copy and paste, or even worse, link to a hosted version of the library, now you fetch a library or module and store it locally in your project. Yarn and NPM work fairly similarly, but have a few key differences in how they operate.

Major Differences Between Yarn & NPM

1. NPM was developed as an open source project in 2009. Yarn was released by Facebook in 2016 as an improvement upon the foundation that NPM laid.
2. Yarn uses yarn add while NPM uses npm install (Can be confusing when switching between the two.)
3. Yarn keeps a copy of packages you download stored locally. I'll explain why in a little bit.
4. Both Yarn and NPM use the package.json file to get the packages to install. However, Yarn uses yarn.lock and NPM uses package-lock.json to more explicitly state which package version to get.

A Breif History of NPM

NPM was originally released back in January 2010 by Isaac Z. Schlueter and took the JavaScript world by storm. It was the inspiration for Yarn, developed by Facebook in 2016, PHP's package manager Composer, and more. Due to the popularity of the project they eventually incorporated as npm, inc in order to manage enterprise level relationships to ensure the success of the project and the JavaScript community as a whole.

Yarn Module Cache

Every time you install a new package with Yarn, it stores a copy of it locally on your computer. This way when multiple projects require the same package, Yarn doesn't have to go download the required package again, it just grabs it off your hard drive and puts it in the project you're installing, saving you time and bandwidth.

Blazing Saddles: Package Manager Boogalo

According to a test done by GitHub user appleboy that you can reproduce yourself, Yarn both with and without it's cache is significantly faster at installing modules, and even installs without internet! (assuming you've cached the package you're installing).

Here are the results of their test comparing NPM to Yarn:

Blazing Fast! Even without using a cache, Yarn is 200% faster than NPM.