https://github.com/github/browser-support
Polyfills & Capable Browser detection
https://github.com/github/browser-support
Last synced: 18 days ago
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Polyfills & Capable Browser detection
- Host: GitHub
- URL: https://github.com/github/browser-support
- Owner: github
- License: mit
- Created: 2022-02-07T09:07:08.000Z (about 4 years ago)
- Default Branch: main
- Last Pushed: 2025-11-10T21:01:11.000Z (4 months ago)
- Last Synced: 2026-02-08T22:41:53.618Z (30 days ago)
- Language: JavaScript
- Homepage: https://github.github.com/browser-support/
- Size: 920 KB
- Stars: 151
- Watchers: 154
- Forks: 34
- Open Issues: 12
-
Metadata Files:
- Readme: README.md
- License: LICENSE
- Codeowners: CODEOWNERS
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README
# browser-support
This library allows websites to maintain compatibility with older browsers, which do not implement newer features. It does so using [polyfills](https://developer.mozilla.org/en-US/docs/Glossary/Polyfill) for small new features, plus functions to determine if a browser supports a set of features natively or with polyfills.
If you would like to see what features the browser you are currently using implements, you [can visit the documentation site](https://github.github.com/browser-support/) which displays a compatibility table that detects which features are natively supported in your browser.
### How is this used on GitHub?
We use all of these polyfills on GitHub.com. We also use the `isSupported()` function to determine if the browser meets a minimum set of functionality which we expect, browser that return false from `isSupported()` do not send errors or statistics to our backend monitoring.
## Installation
```
$ npm install @github/browser-support
```
## Usage
### JS
```js
import {isSupported, isPolyfilled, apply} from '@github/browser-support'
// Check if a browser is supported
if (!isSupported()) {
apply()
console.assert(isSupported() === true)
console.assert(isPolyfilled() === true)
}
```
## Development
```
npm install
npm test
```
## Upgrading browser-support in Dotcom
During upgrades, it is crucial to ensure that browser error reporting to Sentry is not disrupted. Use the following steps to validate this functionality:
### Review lab testing
- Create a PR to upgrade the `browser-support` version in Dotcom.
- Trigger a browser error from your `review-lab` instance and confirm it is reported in Sentry:
- Append `#b00m` to your `review-lab` URL (e.g. `https://branchname.review-lab.github.com#b00m`) and refresh the page.
- Confirm the error is reported in [review-lab Sentry](https://github.sentry.io/issues/?environment=review-lab&groupStatsPeriod=auto&project=1890375&query=b00m&referrer=issue-list&statsPeriod=5m).
- Perform these steps in Chrome, Firefox, Edge, and Opera. Note: Errors are currently not reported in Safari due to an [open issue](https://github.com/github/web-systems/issues/3162).
### Production deployment
- Check the [browser-reporting](https://app.datadoghq.com/monitors/168685099) monitor.
- If the rate of reported browser errors drops, the monitor will trigger an alert in the [#web-systems-ops](https://github-grid.enterprise.slack.com/archives/C046W1V95FV) channel.
- After deploying to canary:
- Trigger a browser error by appending `#b00m` to your URL.
- Confirm the error is reported in [canary Sentry](https://github.sentry.io/issues/?environment=canary&groupStatsPeriod=auto&project=1890375&query=b00m&referrer=issue-list&statsPeriod=5m).
- After deploying to production:
- Trigger a browser error by appending `#b00m` to your URL.
- Confirm the error is reported in [production Sentry](https://github.sentry.io/issues/?environment=production&groupStatsPeriod=auto&project=1890375&query=b00m&referrer=issue-list&statsPeriod=5m).
- Check the [browser-reporting monitor](https://app.datadoghq.com/monitors/168685099) to ensure there are no anomalies in the error reporting rate.
## Contributing
### Adding polyfills
Please do not add any polyfills for ECMA features that are Stage 3 or below. We _only_ wish to polyfill features from ECMAScript that are Stage 4 (about to be included in a new years specification) or already specified.
### Removing polyfills
Polyfills should only be removed after consulting with the `@github/web-systems` who will determine if a polyfill can be removed. This code is designed to be kept lightweight, we do not want to ship dozens of kb of polyfills.
As a polyfill is removed, it may be worth adding feature detection to the `baseSupport` const, to ensure that our baseline moves with our browser support matrix.
## License
Distributed under the MIT license. See LICENSE for details.