browserslist/README.md

# Browserslist

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

Library to share target browsers between different front-end tools.
It is used in:

* [Autoprefixer]
* [babel-preset-env]
  (external config in `package.json` or `browserslist` will be supported in 7.0)
* [postcss-preset-env]
* [eslint-plugin-compat]
* [stylelint-no-unsupported-browser-features]
* [postcss-normalize]

[Browserslist Example] shows how every tool uses Browserslist.
All tools will find target browsers automatically,
when you add the following to `package.json`:

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

Or in `.browserslistrc` config:

```yaml
# 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, `.browserslistrc` config,
`browserslist` section in `package.json` or environment variables.

You can test Browserslist queries in [online demo].

<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/ai/browserslist-example
[postcss-preset-env]:                        https://github.com/jonathantneal/postcss-preset-env
[babel-preset-env]:                          https://github.com/babel/babel/tree/master/packages/babel-preset-env
[postcss-normalize]:                         https://github.com/jonathantneal/postcss-normalize
[Autoprefixer]:                              https://github.com/postcss/autoprefixer
[online demo]:                               http://browserl.ist/
[Can I Use]:                                 http://caniuse.com/

## Tools

* [`browserslist-useragent`] checks browser by user agent string
  to match Browserslist target browsers query.
* [`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`]: https://github.com/pastelsky/browserslist-useragent
[`caniuse-api`]:            https://github.com/Nyalab/caniuse-api


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

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

* `last 2 versions`: the last 2 versions for each browser.
* `last 2 Chrome versions`: the last 2 versions of Chrome browser.
* `> 5%`: 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].
* `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.
* `iOS 7`: the iOS browser version 7 directly.
* `Firefox ESR`: the latest [Firefox ESR] version.
* `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 from `last 2 version` query, but with less than 0.5%
  in global usage statistics and without official support or updates
  for 24 months. Right now it is `IE 10`, `IE_Mob 10`, `BlackBerry 10`,
  and `BlackBerry 7`.
* `defaults`: Browserslist’s default browsers
  (`> 0.5%, last 2 versions, Firefox ESR, not dead`).
* `not ie <= 8`: exclude browsers selected by 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.

```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
```


### Notes

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).

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


### 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.
* `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.


## `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": [
    "> 1%",
    "last 2 versions"
  ]
}
```


## Config File

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

```yaml
# 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.


## 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 2 versions',
  'ie 9'
]
```


## Environment Variables

If some tool use Browserslist inside, you can change browsers settings
by [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


## 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": [
      "last 2 version",
      "ie 9"
    ],
    "development": [
      "last 1 version"
    ]
  }
```

In `.browserslistrc` config:

```ini
[production staging]
last 2 version
ie 9

[development]
last 1 version
```


## 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:

    ```js
   var d=JSON.parse(localStorage["usage-data-by-id"]),e=document.createElement("a");e.setAttribute("href","data:text/plain;charset=utf-8,"+encodeURIComponent(JSON.stringify(d[function(){for(var e in d)return e}()]))),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:

```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.

[Can I Use]: http://caniuse.com/


## JS API

```js
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.

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.`

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

```sh
browserslist "> 1%, last 2 versions"
```


## Coverage

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', { 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" --stats=./browserslist-stats.json
These browsers account for 83.1% of all users in custom statistics
```


## 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.