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Hierarchical node.js configuration with files, environment variables, command-line arguments, and atomic object merging.


Using nconf is easy; it is designed to be a simple key-value store with support for both local and remote storage. Keys are namespaced and delimited by :. Let's dive right into sample usage:

  var fs    = require('fs'),
      nconf = require('nconf');

  // Setup nconf to use (in-order):
  //   1. Command-line arguments
  //   2. Environment variables
  //   3. A file located at 'path/to/config.json'
       .file({ file: 'path/to/config.json' });

  // Set a few variables on `nconf`.
  nconf.set('database:host', '');
  nconf.set('database:port', 5984);

  // Get the entire database object from nconf. This will output
  // { host: '', port: 5984 }
  console.log('foo: ' + nconf.get('foo'));
  console.log('NODE_ENV: ' + nconf.get('NODE_ENV'));
  console.log('database: ' + nconf.get('database'));

  // Save the configuration object to disk
  // (err) {
    fs.readFile('path/to/your/config.json', function (err, data) {

If you run the above script:

  $ NODE_ENV=production sample.js --foo bar

The output will be:

  foo: bar
  NODE_ENV: production
  database: { host: '', port: 5984 }

Hierarchical configuration

Configuration management can get complicated very quickly for even trivial applications running in production. nconf addresses this problem by enabling you to setup a hierarchy for different sources of configuration with no defaults. The order in which you attach these configuration sources determines their priority in the hierarchy. Lets take a look at the options available to you

  1. nconf.argv(options) Loads process.argv using yargs. If options is supplied it is passed along to yargs.
  2. nconf.env(options) Loads process.env into the hierarchy.
  3. nconf.file(options) Loads the configuration data at options.file into the hierarchy.
  4. nconf.defaults(options) Loads the data in into the hierarchy.
  5. nconf.overrides(options) Loads the data in into the hierarchy.

A sane default for this could be:

  var nconf = require('nconf');

  // 1. any overrides
    'always': 'be this value'

  // 2. `process.env`
  // 3. `process.argv`

  // 4. Values in `config.json`

  // Or with a custom name
  // Note: A custom key must be supplied for hierarchy to work if multiple files are used.
  nconf.file('custom', '/path/to/config.json');

  // Or searching from a base directory.
  // Note: `name` is optional.
  nconf.file(name, {
    file: 'config.json',
    dir: 'search/from/here',
    search: true

  // 5. Any default values
    'if nothing else': 'use this value'

API Documentation

The top-level of nconf is an instance of the nconf.Provider abstracts this all for you into a simple API.

nconf.add(name, options)

Adds a new store with the specified name and options. If options.type is not set, then name will be used instead:

  nconf.add('supplied', { type: 'literal', store: { 'some': 'config' });
  nconf.add('user', { type: 'file', file: '/path/to/userconf.json' });
  nconf.add('global', { type: 'file', file: '/path/to/globalconf.json' });

nconf.use(name, options)

Similar to nconf.add, except that it can replace an existing store if new options are provided

  // Load a file store onto nconf with the specified settings
  nconf.use('file', { file: '/path/to/some/config-file.json' });

  // Replace the file store with new settings
  nconf.use('file', { file: 'path/to/a-new/config-file.json' });


Removes the store with the specified name. The configuration stored at that level will no longer be used for lookup(s).


Storage Engines


A simple in-memory storage engine that stores a nested JSON representation of the configuration. To use this engine, just call .use() with the appropriate arguments. All calls to .get(), .set(), .clear(), .reset() methods are synchronous since we are only dealing with an in-memory object.



Responsible for loading the values parsed from process.argv by yargs into the configuration hierarchy. See the yargs option docs for more on the option format.

  // Can optionally also be an object literal to pass to `yargs`.
    "x": {
      alias: 'example',
      describe: 'Example description for usage generation',
      demand: true,
      default: 'some-value'


Responsible for loading the values parsed from process.env into the configuration hierarchy.

  // Can optionally also be an Array of values to limit process.env to.
  nconf.env(['only', 'load', 'these', 'values', 'from', 'process.env']);

  // Can also specify a separator for nested keys (instead of the default ':')
  // Get the value of the env variable 'database__host'
  var dbHost = nconf.get('database:host');

  // Or use all options
    separator: '__',
    match: /^whatever_matches_this_will_be_whitelisted/
    whitelist: ['database__host', 'only', 'load', 'these', 'values', 'if', 'whatever_doesnt_match_but_is_whitelisted_gets_loaded_too']
  var dbHost = nconf.get('database:host');


Loads a given object literal into the configuration hierarchy. Both nconf.defaults() and nconf.overrides() use the Literal store.

    'some': 'default value'


Based on the Memory store, but provides additional methods .save() and .load() which allow you to read your configuration to and from file. As with the Memory store, all method calls are synchronous with the exception of .save() and .load() which take callback functions. It is important to note that setting keys in the File engine will not be persisted to disk until a call to .save() is made. Note a custom key must be supplied as the first parameter for hierarchy to work if multiple files are used.

  // add multiple files, hierarchically. notice the unique key for each file
  nconf.file('user', 'path/to/your/user.json');
  nconf.file('global', 'path/to/your/global.json');

The file store is also extensible for multiple file formats, defaulting to JSON. To use a custom format, simply pass a format object to the .use() method. This object must have .parse() and .stringify() methods just like the native JSON object.

If the file does not exist at the provided path, the store will simply be empty.


There is a separate Redis-based store available through nconf-redis. To install and use this store simply:

  $ npm install nconf
  $ npm install nconf-redis

Once installing both nconf and nconf-redis, you must require both modules to use the Redis store:

  var nconf = require('nconf');

  // Requiring `nconf-redis` will extend the `nconf`
  // module.

  nconf.use('redis', { host: 'localhost', port: 6379, ttl: 60 * 60 * 1000 });


Installing npm (node package manager)

  curl | sh

Installing nconf

  [sudo] npm install nconf

More Documentation

There is more documentation available through docco. I haven't gotten around to making a gh-pages branch so in the meantime if you clone the repository you can view the docs:

  open docs/nconf.html

Run Tests

Tests are written in vows and give complete coverage of all APIs and storage engines.

  $ npm test

Author: Charlie Robbins

License: MIT