You can add a package.json file to your package to make it easy for others to manage and install. Packages published to the registry must contain a package.json file.

A package.json file:

• lists the packages your project depends on
• specifies versions of a package that your project can use using semantic versioning rules
• makes your build reproducible, and therefore easier to share with other developers

package.json fields

Required name and version fields

A package.json file must contain "name" and "version" fields.

The "name" field contains your package's name, and must be lowercase and one word, and may contain hyphens and underscores.

The "version" field must be in the form x.x.x and follow the semantic versioning guidelines.

Author field

If you want to include package author information in "author" field, use the following format (email and website are both optional):

Your Name <[email protected]> (http://example.com)

Example

{
  "name": "my-awesome-package",
  "version": "1.0.0",
  "author": "Your Name <[email protected]>"
}

Creating a new package.json file

You can create a package.json file by running a CLI questionnaire or creating a default package.json file.

Running a CLI questionnaire

To create a package.json file with values that you supply, use the npm init command.

1. On the command line, navigate to the root directory of your package.

   cd /path/to/package

2. Run the following command:

   npm init

3. Answer the questions in the command line questionnaire.

Customizing the package.json questionnaire

If you expect to create many package.json files, you can customize the questions asked and fields created during the init process so all the package.json files contain a standard set of information.

1. In your home directory, create a file called .npm-init.js.

2. To add custom questions, using a text editor, add questions with the prompt function:

   module.exports = prompt("what's your favorite flavor of ice cream, buddy?", "I LIKE THEM ALL");

3. To add custom fields, using a text editor, add desired fields to the .npm-init.js file:

   module.exports = {
     customField: 'Example custom field',
     otherCustomField: 'This example field is really cool'
   }

To learn more about creating advanced npm init customizations, see the init-package-json GitHub repository.

Creating a default package.json file

To create a default package.json using information extracted from the current directory, use the npm init command with the --yes or -y flag. For a list of default values, see "Default values extracted from the current directory".

1. On the command line, navigate to the root directory of your package.

   cd /path/to/package

2. Run the following command:

   npm init --yes

Example

> npm init --yes
Wrote to /home/monatheoctocat/my_package/package.json:

{
  "name": "my_package",
  "description": "",
  "version": "1.0.0",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "repository": {
    "type": "git",
    "url": "https://github.com/monatheoctocat/my_package.git"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "bugs": {
    "url": "https://github.com/monatheoctocat/my_package/issues"
  },
  "homepage": "https://github.com/monatheoctocat/my_package"
}

Default values extracted from the current directory

• name: the current directory name
• version: always 1.0.0
• description: info from the README, or an empty string ""
• scripts: by default creates an empty test script
• keywords: empty
• author: empty
• license: ISC
• bugs: information from the current directory, if present
• homepage: information from the current directory, if present

Setting config options for the init command

You can set default config options for the init command. For example, to set the default author email, author name, and license, on the command line, run the following commands:

> npm set init-author-email "[email protected]"
> npm set init-author-name "example_user"
> npm set init-license "MIT"