notes/node_modules/browserslist/README.md

Browserslist

Library to share supported browsers list between different front-end tools. It is used in Autoprefixer, Stylelint, eslint-plugin-compat and babel-env-preset.

All tools that rely on Browserslist will find its config automatically, when you add the following to package.json:

{
  "browserslist": [
    "> 1%",
    "last 2 versions"
  ]
}

Or in browserslist config:

# Browsers that we support

> 1%
Last 2 versions
IE 10 # sorry

Developers set browsers list in queries like last 2 version to be free from updating browser versions manually. Browserslist will use Can i Use data for this queries.

Browserslist will take browsers queries from tool option, browserslist config, browserslist section in package.json or environment variables.

You can test Browserslist queries in online demo.

Queries

Browserslist will use browsers query from one of this sources:

1. Tool options. For example browsers option in Autoprefixer.
2. BROWSERSLIST environment variable.
3. browserslist config file in current or parent directories.
4. browserslist key in package.json file in current or parent directories.
5. If the above methods did not produce a valid result Browserslist will use defaults: > 1%, last 2 versions, Firefox ESR.

We recommends to write queries in browserslist config or package.json.

You can specify the versions by queries (case insensitive):

• last 2 versions: the last 2 versions for each major browser.
• last 2 Chrome versions: the last 2 versions of Chrome browser.
• > 5%: versions selected by global usage statistics.
• > 5% in US: uses USA usage statistics. It accepts two-letter country code.
• > 5% in my stats: uses custom usage data.
• ie 6-8: selects an inclusive range of versions.
• Firefox > 20: versions of Firefox newer than 20.
• Firefox >= 20: versions of Firefox newer than or equal to 20.
• Firefox < 20: versions of Firefox less than 20.
• Firefox <= 20: versions of Firefox less than or equal to 20.
• Firefox ESR: the latest [Firefox ESR] version.
• iOS 7: the iOS browser version 7 directly.
• not ie <= 8: exclude browsers selected before by previous queries. You can add not to any query.

Browserslist works with separated versions of browsers. You should avoid queries like Firefox > 0.

Multiple criteria are combined as a boolean OR. A browser version must match at least one of the criteria to be selected.

All queries are based on the Can I Use support table, e.g. last 3 iOS versions might select 8.4, 9.2, 9.3 (mixed major and minor), whereas last 3 Chrome versions might select 50, 49, 48 (major only).

Browsers

Names are case insensitive:

Major Browsers

• Chrome for Google Chrome.
• Firefox or ff for Mozilla Firefox.
• Explorer or ie for Internet Explorer.
• Edge for Microsoft Edge.
• iOS or ios_saf for iOS Safari.
• Opera for Opera.
• Safari for desktop Safari.
• ExplorerMobile or ie_mob for Internet Explorer Mobile.

Others

• Android for Android WebView.
• BlackBerry or bb for Blackberry browser.
• ChromeAndroid or and_chr for Chrome for Android (in Other section, because mostly same as common Chrome).
• FirefoxAndroid or and_ff for Firefox for Android.
• OperaMobile or op_mob for Opera Mobile.
• OperaMini or op_mini for Opera Mini.
• Samsung for Samsung Internet.
• UCAndroid or and_uc for UC Browser for Android.
• Electron for Electron framework. It will be converted to Chrome version.

Electron

electron-to-chromium could return a compatible Browserslist query for your (major) Electron version:

const e2c = require('electron-to-chromium')
autoprefixer({
    browsers: e2c.electronToBrowserList('1.4') //=> "Chrome >= 53"
})

Config File

Browserslist config should be named browserslist and have browsers queries split by a new line. Comments starts with # symbol:

# Browsers that we support

> 1%
Last 2 versions
IE 8 # sorry

Browserslist will check config in every directory in path. So, if tool process app/styles/main.css, you can put config to root, app/ or app/styles.

You can specify direct path in BROWSERSLIST_CONFIG environment variables.

package.json

If you want to reduce config files in project root, you can specify browsers in package.json with browserslist key:

{
  "private": true,
  "dependencies": {
    "autoprefixer": "^6.5.4"
  },
  "browserslist": [
    "> 1%",
    "last 2 versions"
  ]
}

Environments

You can also specify different browser queries for various environments. Browserslist will choose query according to BROWSERSLIST_ENV or NODE_ENV variables. If none of them is declared, Browserslist will firstly look for development queries and then use defaults.

In package.json:

{
  …
  "browserslist": {
    "production": [
      "last 2 version",
      "ie 9"
    ],
    "development": [
      "last 1 version"
    ]
  }
}

In browserslist config:

[production]
last 2 version
ie 9

[development]
last 1 version

Environment Variables

If some tool use Browserslist inside, you can change browsers settings by environment variables:

• BROWSERSLIST with browsers queries.

  BROWSERSLIST="> 5%" gulp css
  

• BROWSERSLIST_CONFIG with path to config file.

  BROWSERSLIST_CONFIG=./config/browserslist gulp css
  

• BROWSERSLIST_ENV with environments string.

  BROWSERSLIST_ENV="development" gulp css
  

• BROWSERSLIST_STATS with path to the custom usage data for > 1% in my stats query.

  BROWSERSLIST_STATS=./config/usage_data.json gulp css
  

Custom Usage Data

If you have a website, you can query against the usage statistics of your site:

1. Import your Google Analytics data into Can I Use. Press Import… button in Settings page.

2. Open browser DevTools on Can I Use and paste this snippet into the browser console:

   var e=document.createElement('a');e.setAttribute('href', 'data:text/plain;charset=utf-8,'+encodeURIComponent(JSON.stringify(JSON.parse(localStorage['usage-data-by-id'])[localStorage['config-primary_usage']])));e.setAttribute('download','stats.json');document.body.appendChild(e);e.click();document.body.removeChild(e);
   

3. Save the data to a browserslist-stats.json file in your project.

Of course, you can generate usage statistics file by any other method. File format should be like:

{
  "ie": {
    "6": 0.01,
    "7": 0.4,
    "8": 1.5
  },
  "chrome": {
    …
  },
  …
}

Note that you can query against your custom usage data while also querying against global or regional data. For example, the query > 1% in my stats, > 5% in US, 10% is permitted.

JS API

var browserslist = require('browserslist');

// Your CSS/JS build tool code
var process = function (source, opts) {
    var browsers = browserslist(opts.browsers, {
        stats: opts.stats,
        path:  opts.file,
        env:   opts.env
    });
    // Your code to add features for selected browsers
}

Queries can be a string "> 5%, last 1 version" or an array ['> 5%', 'last 1 version'].

If a query is missing, Browserslist will look for a config file. You can provide a path option (that can be a file) to find the config file relatively to it.

For non-JS environment and debug purpose you can use CLI tool:

browserslist "> 1%, last 2 versions"

Coverage

You can get total users coverage for selected browsers by JS API:

browserslist.coverage(browserslist('> 1%')) //=> 81.4

browserslist.coverage(browserslist('> 1% in US'), 'US') //=> 83.1

Or by CLI:

$ browserslist --coverage "> 1%"
These browsers account for 81.4% of all users globally

$ browserslist --coverage=US "> 1% in US"
These browsers account for 83.1% of all users in the US