Difference between dependencies, devDependencies and peerDependencies - GeeksforGeeks (2024)

Dependencies are part of the project required to run the project, devDependencies are only required for the development while peerDependencies specifies the compatible versions of the packages to be used in the project.

Every web application project typically includes a file named package.json, which serves as a repository of essential project metadata. This file encompasses information ranging from dependencies and their respective versions to development dependencies and peer dependencies.

Run the following command to initialize the project from the root directory of your project:

npm init -y

Dependencies

In the package.json file, there is an object called dependencies and it consists of all the packages that are used in the project with its version number. So, whenever you install any library that is required in your project that library you can find it in the dependencies object.

Syntax:

npm install <package name>

Example: Installing the moment module for formatting the time in the project using the following command:

npm install moment

After the module is installed, then if you navigate to the package.json file then you can find the moment with its version in the dependencies object as shown below:

package.json:

"dependencies": { 
 "moment": "^2.30.1",
}

devDependencies

In package.json file, there is an object called as dev Dependencies and it consists of all the packages that are used in the project in its development phase and not in the production or testing environment with its version number. So, whenever you want to install any library that is required only in your development phase then you can find it in the dev Dependencies object.

Use the below command to add more dev Dependencies in your project:

npm install <package name> --save-dev

Example: Installing the bootstrap module that we want to use in the development phase only and not in the production or testing phase for the project, use the following command:

npm install bootstrap --save-dev

package.json:

"devDependencies": {
 "bootstrap": "^5.3.2",
}

peerDependencies

In package.json file, there is an object called as peerDependencies and it consists of all the packages that are exactly required in the project or to the person who is downloading and the version numbers should also be the same. That is the reason they were named as peerDependencies. The best example is ‘react’ which is common in every project to run similarly.

Note: These dependencies are not automatically installed. npm gives a warning message whenever there is a peer Dependency and these are different dependencies compared to the above-discussed dependencies.

Difference between Dependencies, devDependencies and peerDependencies

npm i <package_name>

npm i <package_name> 
--save-dev

Conclusion

In a web development project Dependencies are needed for production, devDependencies are for development only, and peerDependencies ensure compatibility with specific versions of other packages, often used by plugins or shared libraries.