node package manager



A config module which only reads the environment. For Node.js that means process.env.

Note 1 : We will not ever use NODE_ENV in any example here since each environment should specify everything it needs and nothing should be dependent on being a particular environment (such as 'development', 'testing', 'staging' or 'production').

Note 2 : This package is considered stable so the fact that there are few commits these days is no sign of inactivity, just stability. Please use and submit PRs for bugs. New features will be considered too.


Please note that this project is pretty much feature complete. Issues will be fixed. New features may be added if necessary. Otherwise it won't have very many more releases - but rest assured I will support it and you. The project is not dead, it is merely resting.


Firstly, set some environment variables that your program will look for. You don't need to set any that have a 'default' but you do need to set any that are 'required'.

$ export REDIS_URL=redis://user:password@hostname:port/db
$ export APPNAME_PORT=8080

Then, in your program:

var config = require('12factor-config');
var cfg = config({
    redisUrl : {
        env      : 'REDIS_URL',
        type     : 'string', // default 
        required : true,
    logfile : {
        env      : 'APPNAME_LOG_FILE',
        type     : 'string',
        default  : '/var/log/appname.log',
        required : true,
    port : {
        env      : 'APPNAME_PORT',
        type     : 'integer',
        default  : '8000',
        required : true,
    debug : {
        env      : 'APPNAME_DEBUG',
        type     : 'boolean',
        default  : false,
    env : {
        // you really shouldn't use this, but some people/packages do 
        env      : 'NODE_ENV',
        type     : 'enum',
        values   : [ 'development', 'test', 'stage', 'production', ],

Should output something like:

  redisUrl: 'redis://user:password@hostname:port/db',
  logfile: '/var/log/appname.log',
  port: 8080,
  debug: false,
  env: 'development'

It is advisable to prefix your environment variables with a prefix related to your application name as shown in the later config vars above. Mainly this is to namespace your vars and not stomp over others already defined. Of course you don't need to use the prefix in the local name.

Valid Values

When you have certain types, some transformations are performed to get it from a string (since the environment only contains string) into the required value.

  • boolean - upper or lower case is allowed
    • true - 'true', 't', 'yes', 'y', 'on', '1'
    • false - 'false', 'f', 'no', 'n', 'off', '0'
    • any other value throws

What I Do

I usually have a lib/cfg.js such as the following:

var config = require('12factor-config');
var cfg = config({
    // ... environment config here ... 
module.exports = cfg;

By doing this, all other files in your application can just require('lib/cfg.js') and obtain the exact same configuration.


Written by Andrew Chilton - Blog - Twitter.