browserslist/README.md

# Browserslist [![Cult Of Martians][cult-img]][cult]

<img width="120" height="120" alt="Browserslist logo by Anton Lovchikov"
     src="https://browserslist.github.io/browserslist/logo.svg" align="right">

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

* [Autoprefixer]
* [Babel]
* [postcss-preset-env]
* [eslint-plugin-compat]
* [stylelint-no-unsupported-browser-features]
* [postcss-normalize]
* [obsolete-webpack-plugin]

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

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

Or in `.browserslistrc` config:

```yaml
# Browsers that we support

defaults
not IE 11
not IE_Mob 11
maintained node versions
```

Developers set their version lists using queries like `last 2 version`
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.

[Browserslist Example] shows how every tool uses Browserslist.

[cult-img]: https://cultofmartians.com/assets/badges/badge.svg
[cult]: https://cultofmartians.com/done.html

<a href="https://evilmartians.com/?utm_source=browserslist">
  <img src="https://evilmartians.com/badges/sponsored-by-evil-martians.svg"
       alt="Sponsored by Evil Martians" width="236" height="54">
</a>

[stylelint-no-unsupported-browser-features]: https://github.com/ismay/stylelint-no-unsupported-browser-features
[eslint-plugin-compat]:                      https://github.com/amilajack/eslint-plugin-compat
[Browserslist Example]:                      https://github.com/browserslist/browserslist-example
[postcss-preset-env]:                        https://github.com/jonathantneal/postcss-preset-env
[postcss-normalize]:                         https://github.com/jonathantneal/postcss-normalize
[`caniuse-lite`]:                            https://github.com/ben-eb/caniuse-lite
[Autoprefixer]:                              https://github.com/postcss/autoprefixer
[Can I Use]:                                 https://caniuse.com/
[Babel]:                                     https://github.com/babel/babel/tree/master/packages/babel-preset-env
[obsolete-webpack-plugin]:                   https://github.com/ElemeFE/obsolete-webpack-plugin

## Table of Contents

1. [Tools](#tools)
2. [Best Practices](#best-practices)
3. [Queries](#queries)
4. [Config File](#config-file)
5. [Shareable Configs](#shareable-configs)
6. [Configuring for Different Environments](#configuring-for-different-environments)
7. [Custom Usage Data](#custom-usage-data)
8. [JS API](#js-api)
9. [Environment Variables](#environment-variables)
10. [Cache](#cache)

## Tools

* [`browserl.ist`](https://browserl.ist/) is an online tool to check
  what browsers will be selected by some query.
* [`browserslist-ga`] and [`browserslist-ga-export`] download your website
  browsers statistics to use it in `> 0.5% in my stats` query.
* [`browserslist-useragent-regexp`] compiles Browserslist query to a RegExp
  to test browser useragent.
* [`browserslist-useragent-ruby`] is a Ruby library to checks browser
  by user agent string to match Browserslist.
* [`browserslist-browserstack`] runs BrowserStack tests for all browsers
  in Browserslist config.
* [`caniuse-api`] returns browsers which support some specific feature.
* Run `npx browserslist` in your project directory to see project’s
  target browsers. This CLI tool is built-in and available in any project
  with Autoprefixer.

[`browserslist-useragent-regexp`]: https://github.com/browserslist/browserslist-useragent-regexp
[`browserslist-useragent-ruby`]:   https://github.com/browserslist/browserslist-useragent-ruby
[`browserslist-browserstack`]:     https://github.com/xeroxinteractive/browserslist-browserstack
[`browserslist-ga-export`]:        https://github.com/browserslist/browserslist-ga-export
[`browserslist-useragent`]:        https://github.com/pastelsky/browserslist-useragent
[`browserslist-ga`]:               https://github.com/browserslist/browserslist-ga
[`caniuse-api`]:                   https://github.com/Nyalab/caniuse-api


## Best Practices

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

  ```json
    "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.


## 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 the previous query: `last 1 version and > 1%`.

There is 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.

| Query combiner type | Illustration | Example |
| ------------------- | :----------: | ------- |
|`or`/`,` combiner <br> (union) | ![Union of queries](img/union.svg)  | `> .5% or last 2 versions` <br> `> .5%, last 2 versions` |
| `and` combiner <br> (intersection) | ![intersection of queries](img/intersection.svg) | `> .5% and last 2 versions` |
| `not` combiner <br> (relative complement) | ![Relative complement of queries](img/complement.svg) | `> .5% and not last 2 versions` <br> `> .5% or not last 2 versions` <br> `> .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`).
* `> 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].
* `maintained node versions`: all Node.js versions, which are [still maintained]
  by Node.js Foundation.
* `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.
* `extends browserslist-config-mycompany`: take queries from
  `browserslist-config-mycompany` npm package.
* `ie 6-8`: selects an inclusive range of versions.
* `Firefox > 20`: versions of Firefox newer than 20.
  `>=`, `<` and `<=` work too. It also works with Node.js.
* `iOS 7`: the iOS browser version 7 directly.
* `Firefox ESR`: the latest [Firefox ESR] version.
* `PhantomJS 2.1` and `PhantomJS 1.9`: selects Safari versions similar
  to PhantomJS runtime.
* `unreleased versions` or `unreleased Chrome versions`:
  alpha and beta versions.
* `last 2 major versions` or `last 2 iOS major versions`:
  all minor/patch releases of last 2 major versions.
* `since 2015` or `last 2 years`: all versions released since year 2015
  (also `since 2015-03` and `since 2015-03-10`).
* `dead`: browsers without official support or updates for 24 months.
  Right now it is `IE 10`, `IE_Mob 10`, `BlackBerry 10`, `BlackBerry 7`,
  `Samsung 4` and `OperaMobile 12.1`.
* `last 2 versions`: the last 2 versions for *each* browser.
* `last 2 Chrome versions`: the last 2 versions of Chrome browser.
* `not ie <= 8`: exclude browsers selected by previous queries.

You can add `not ` to any query.

[`caniuse-lite/data/regions`]: https://github.com/ben-eb/caniuse-lite/tree/master/data/regions
[two-letter country code]:     https://en.wikipedia.org/wiki/ISO_3166-1_alpha-2#Officially_assigned_code_elements
[custom usage data]:           #custom-usage-data
[still maintained]:            https://github.com/nodejs/Release
[Can I Use]:                   https://caniuse.com/


### Debug

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

```sh
$ 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:

```json
{
  "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. Comments starts with `#` symbol:

```yaml
# 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:

```json
  "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 `dangerousExtend` option:

```js
browserslist(queries, { path, dangerousExtend: true })
```

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

```json
  "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`:

```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.


## 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`:

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

In `.browserslistrc` config:

```ini
[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:

```js
{
  "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.

[`browserslist-ga-export`]: https://github.com/browserslist/browserslist-ga-export
[`browserslist-ga`]:        https://github.com/browserslist/browserslist-ga
[Can I Use]:                https://caniuse.com/


## JS API

```js
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:

```sh
browserslist "> 1%, IE 10"
```

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

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

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

```js
browserslist.coverage(browserslist('> 1% in my stats'), 'my stats')
//=> 83.1
```

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

Or by CLI:

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

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

```sh
$ browserslist --coverage "> 1% in my stats"
These browsers account for 83.1% of all users in custom statistics
```

```sh
$ 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.

   ```sh
  BROWSERSLIST="> 5%" gulp css
   ```

* `BROWSERSLIST_CONFIG` with path to config file.

   ```sh
  BROWSERSLIST_CONFIG=./config/browserslist gulp css
   ```

* `BROWSERSLIST_ENV` with environments string.

   ```sh
  BROWSERSLIST_ENV="development" gulp css
   ```

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

   ```sh
  BROWSERSLIST_STATS=./config/usage_data.json gulp css
   ```

* `BROWSERSLIST_DISABLE_CACHE` if you want to disable config reading cache.

   ```sh
  BROWSERSLIST_DISABLE_CACHE=1 gulp css
   ```

[environment variables]: https://en.wikipedia.org/wiki/Environment_variable


## 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:

```js
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.

[Tidelift security contact]: https://tidelift.com/security