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Browserslist Cult Of Martians

Browserslist logo by Anton Lovchikov

The config to share target browsers and Node.js versions between different front-end tools. It is used in:

All tools will find target browsers automatically, when you add the following to package.json:

  "browserslist": [
    "defaults",
    "not IE 11",
    "maintained node versions"
  ]

Or in .browserslistrc config:

# Browsers that we support

defaults
not IE 11
maintained node versions

Developers set their version lists using queries like last 2 versions to be free from updating versions manually. Browserslist will use caniuse-lite with [Can I Use] data for this queries.

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

Sponsored by Evil Martians

Table of Contents

Tools

Text Editors

These extensions will add syntax highlighting for .browserslistrc files.

Best Practices

  • There is a defaults query, which gives a reasonable configuration for most users:

      "browserslist": [
    "defaults"
  ]

  • If you want to change the default set of browsers, we recommend combining last 2 versions, not dead with a usage number like > 0.2%. This is because last n versions on its own does not add popular old versions, while only using a percentage above 0.2% will in the long run make popular browsers even more popular. We might run into a monopoly and stagnation situation, as we had with Internet Explorer 6. Please use this setting with caution.

  • Select browsers directly (last 2 Chrome versions) only if you are making a web app for a kiosk with one browser. There are a lot of browsers on the market. If you are making general web app you should respect browsers diversity.
  • Don’t remove browsers just because you don’t know them. Opera Mini has 100 million users in Africa and it is more popular in the global market than Microsoft Edge. Chinese QQ Browsers has more market share than Firefox and desktop Safari combined.

Browsers Data Updating

npx browserslist@latest --update-db updates caniuse-lite version in your npm, yarn or pnpm lock file.

You need to do it regularly for two reasons:

  1. To use the latest browser’s versions and statistics in queries like last 2 versions or >1%. For example, if you created your project 2 years ago and did not update your dependencies, last 1 version will return 2 year old browsers.
  2. caniuse-lite deduplication: to synchronize version in different tools.

What is deduplication?

Due to how npm architecture is setup, you may have a situation where you have multiple versions of a single dependency required.

Imagine you begin a project, and you add autoprefixer as a dependency. npm looks for the latest caniuse-lite version (1.0.30000700) and adds it to package-lock.json under autoprefixer dependencies.

A year later, you decide to add Babel. At this moment, we have a new version of canuse-lite (1.0.30000900). npm took the latest version and added it to your lock file under @babel/preset-env dependencies.

Now your lock file looks like this:

autoprefixer 7.1.4
  browserslist 3.1.1
    caniuse-lite 1.0.30000700
@babel/preset-env 7.10.0
  browserslist 4.13.0
    caniuse-lite 1.0.30000900

As you can see, we now have two versions of caniuse-lite installed.

Queries

Browserslist will use browsers and Node.js versions query from one of these sources:

  1. browserslist key in package.json file in current or parent directories. We recommend this way.
  2. .browserslistrc config file in current or parent directories.
  3. browserslist config file in current or parent directories.
  4. BROWSERSLIST environment variable.
  5. If the above methods did not produce a valid result Browserslist will use defaults: > 0.5%, last 2 versions, Firefox ESR, not dead.

Query Composition

An or combiner can use the keyword or as well as ,. last 1 version or > 1% is equal to last 1 version, > 1%.

and query combinations are also supported to perform an intersection of all the previous queries: last 1 version or chrome > 75 and > 1% will select (browser last version or Chrome since 76) and more than 1% marketshare.

There are 3 different ways to combine queries as depicted below. First you start with a single query and then we combine the queries to get our final list.

Obviously you can not start with a not combiner, since there is no left-hand side query to combine it with. The left-hand is always resolved as and combiner even if or is used (this is an API implementation specificity).

Query combiner type Illustration Example
or/, combiner
(union)		 Union of queries > .5% or last 2 versions
> .5%, last 2 versions
and combiner
(intersection)		 intersection of queries > .5% and last 2 versions
not combiner
(relative complement)		 Relative complement of queries All those three are equivalent to the first one
> .5% and not last 2 versions
> .5% or not last 2 versions
> .5%, not last 2 versions

A quick way to test your query is to do npx browserslist '> 0.5%, not IE 11' in your terminal.

Full List

You can specify the browser and Node.js versions by queries (case insensitive):

  • defaults: Browserslist’s default browsers (> 0.5%, last 2 versions, Firefox ESR, not dead).
  • By usage statistics:
    • > 5%: browsers versions selected by global usage statistics. >=, < and <= work too.
    • > 5% in US: uses USA usage statistics. It accepts [two-letter country code].
    • > 5% in alt-AS: uses Asia region usage statistics. List of all region codes can be found at caniuse-lite/data/regions.
    • > 5% in my stats: uses [custom usage data].
    • > 5% in browserslist-config-mycompany stats: uses [custom usage data] from browserslist-config-mycompany/browserslist-stats.json.
    • cover 99.5%: most popular browsers that provide coverage.
    • cover 99.5% in US: same as above, with [two-letter country code].
    • cover 99.5% in my stats: uses [custom usage data].
  • Last versions:
    • last 2 versions: the last 2 versions for each browser.
    • last 2 Chrome versions: the last 2 versions of Chrome browser.
    • last 2 major versions or last 2 iOS major versions: all minor/patch releases of last 2 major versions.
  • dead: browsers without official support or updates for 24 months. Right now it is IE 10, IE_Mob 11, BlackBerry 10, BlackBerry 7, Samsung 4 and OperaMobile 12.1.
  • Node.js versions:
    • node 10 and node 10.4: selects latest Node.js 10.x.x or 10.4.x release.
    • current node: Node.js version used by Browserslist right now.
    • maintained node versions: all Node.js versions, which are [still maintained] by Node.js Foundation.
  • Browsers versions:
    • iOS 7: the iOS browser version 7 directly.
    • Firefox > 20: versions of Firefox newer than 20. >=, < and <= work too. It also works with Node.js.
    • ie 6-8: selects an inclusive range of versions.
    • Firefox ESR: the latest [Firefox Extended Support Release].
    • PhantomJS 2.1 and PhantomJS 1.9: selects Safari versions similar to PhantomJS runtime.
  • extends browserslist-config-mycompany: take queries from browserslist-config-mycompany npm package.
  • supports es6-module: browsers with support for specific features. es6-module here is the feat parameter at the URL of the [Can I Use] page. A list of all available features can be found at caniuse-lite/data/features.
  • browserslist config: the browsers defined in Browserslist config. Useful in Differential Serving to modify user’s config like browserslist config and supports es6-module.
  • since 2015 or last 2 years: all versions released since year 2015 (also since 2015-03 and since 2015-03-10).
  • unreleased versions or unreleased Chrome versions: alpha and beta versions.
  • not ie <= 8: exclude IE 8 and lower from previous queries.

You can add not to any query.

Debug

Run npx browserslist in project directory to see what browsers was selected by your queries.

$ npx browserslist
and_chr 61
and_ff 56
and_qq 1.2
and_uc 11.4
android 56
baidu 7.12
bb 10
chrome 62
edge 16
firefox 56
ios_saf 11
opera 48
safari 11
samsung 5

Browsers

Names are case insensitive:

  • Android for Android WebView.
  • Baidu for Baidu Browser.
  • BlackBerry or bb for Blackberry browser.
  • Chrome for Google Chrome.
  • ChromeAndroid or and_chr for Chrome for Android
  • Edge for Microsoft Edge.
  • Electron for Electron framework. It will be converted to Chrome version.
  • Explorer or ie for Internet Explorer.
  • ExplorerMobile or ie_mob for Internet Explorer Mobile.
  • Firefox or ff for Mozilla Firefox.
  • FirefoxAndroid or and_ff for Firefox for Android.
  • iOS or ios_saf for iOS Safari.
  • Node for Node.js.
  • Opera for Opera.
  • OperaMini or op_mini for Opera Mini.
  • OperaMobile or op_mob for Opera Mobile.
  • QQAndroid or and_qq for QQ Browser for Android.
  • Safari for desktop Safari.
  • Samsung for Samsung Internet.
  • UCAndroid or and_uc for UC Browser for Android.
  • kaios for KaiOS Browser.

Config File

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": [
    "last 1 version",
    "> 1%",
    "IE 10"
  ]
}

.browserslistrc

Separated Browserslist config should be named .browserslistrc and have browsers queries split by a new line. Each line is combined with the or combiner. Comments starts with # symbol:

# Browsers that we support

last 1 version
> 1%
IE 10 # 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.

Shareable Configs

You can use the following query to reference an exported Browserslist config from another package:

  "browserslist": [
    "extends browserslist-config-mycompany"
  ]

For security reasons, external configuration only supports packages that have the browserslist-config- prefix. npm scoped packages are also supported, by naming or prefixing the module with @scope/browserslist-config, such as @scope/browserslist-config or @scope/browserslist-config-mycompany.

If you don’t accept Browserslist queries from users, you can disable the validation by using the or BROWSERSLIST_DANGEROUS_EXTEND environment variable.

BROWSERSLIST_DANGEROUS_EXTEND=1 npx webpack

Because this uses npm's resolution, you can also reference specific files in a package:

  "browserslist": [
    "extends browserslist-config-mycompany/desktop",
    "extends browserslist-config-mycompany/mobile"
  ]

When writing a shared Browserslist package, just export an array. browserslist-config-mycompany/index.js:

module.exports = [
  'last 1 version',
  '> 1%',
  'ie 10'
]

You can also include a browserslist-stats.json file as part of your shareable config at the root and query it using > 5% in browserslist-config-mycompany stats. It uses the same format as extends and the dangerousExtend property as above.

You can export configs for different environments and select environment by BROWSERSLIST_ENV or env option in your tool:

module.exports = {
  development: [
    'last 1 version'
  ],
  production: [
    'last 1 version',
    '> 1%',
    'ie 10'
  ]
}

Configuring for Different 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 production queries and then use defaults.

In package.json:

  "browserslist": {
    "production": [
      "> 1%",
      "ie 10"
    ],
    "modern": [
      "last 1 chrome version",
      "last 1 firefox version"
    ],
    "ssr": [
      "node 12"
    ]
  }

In .browserslistrc config:

[production]
> 1%
ie 10

[modern]
last 1 chrome version
last 1 firefox version

[ssr]
node 12

Custom Usage Data

If you have a website, you can query against the usage statistics of your site. browserslist-ga will ask access to Google Analytics and then generate browserslist-stats.json:

npx browserslist-ga

Or you can use browserslist-ga-export to convert Google Analytics data without giving a password for Google account.

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

const browserslist = require('browserslist')

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

Queries can be a string "> 1%, IE 10" or an array ['> 1%', 'IE 10'].

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.

Options:

  • path: file or a directory path to look for config file. Default is ..
  • env: what environment section use from config. Default is production.
  • stats: custom usage statistics data.
  • config: path to config if you want to set it manually.
  • ignoreUnknownVersions: do not throw on direct query (like ie 12). Default is false.
  • dangerousExtend: Disable security checks for extend query. Default is false.
  • mobileToDesktop: Use desktop browsers if Can I Use doesn’t have data about this mobile version. For instance, Browserslist will return chrome 20 on and_chr 20 query (Can I Use has only data only about latest versions of mobile browsers). Default is false.

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

browserslist "> 1%, IE 10"

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
browserslist.coverage(browserslist('> 1% in my stats'), 'my stats')
//=> 83.1
browserslist.coverage(browserslist('> 1% in my stats', { stats }), stats)
//=> 82.2

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
$ browserslist --coverage "> 1% in my stats"
These browsers account for 83.1% of all users in custom statistics
$ browserslist --coverage "> 1% in my stats" --stats=./stats.json
These browsers account for 83.1% of all users in custom statistics

Environment Variables

If a tool uses Browserslist inside, you can change the Browserslist settings with [environment variables]:

  • BROWSERSLIST with browsers queries.

    BROWSERSLIST="> 5%" npx webpack

  • BROWSERSLIST_CONFIG with path to config file.

    BROWSERSLIST_CONFIG=./config/browserslist npx webpack

  • BROWSERSLIST_ENV with environments string.

    BROWSERSLIST_ENV="development" npx webpack

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

    BROWSERSLIST_STATS=./config/usage_data.json npx webpack

  • BROWSERSLIST_DISABLE_CACHE if you want to disable config reading cache.

    BROWSERSLIST_DISABLE_CACHE=1 npx webpack

  • BROWSERSLIST_DANGEROUS_EXTEND to disable security shareable config name check.

    BROWSERSLIST_DANGEROUS_EXTEND=1 npx webpack

Cache

Browserslist caches the configuration it reads from package.json and browserslist files, as well as knowledge about the existence of files, for the duration of the hosting process.

To clear these caches, use:

browserslist.clearCaches()

To disable the caching altogether, set the BROWSERSLIST_DISABLE_CACHE environment variable.

Security Contact

To report a security vulnerability, please use the [Tidelift security contact]. Tidelift will coordinate the fix and disclosure.

For Enterprise

Available as part of the Tidelift Subscription.

The maintainers of browserslist and thousands of other packages are working with Tidelift to deliver commercial support and maintenance for the open source dependencies you use to build your applications. Save time, reduce risk, and improve code health, while paying the maintainers of the exact dependencies you use. Learn more.