isMobile
A simple JS library that detects mobile devices in both the browser and NodeJS.
Why use isMobile?
In the Browser
You might not need this library. In most cases, responsive design solves the problem of controlling how to render things across different screen sizes. I recommend a mobile first approach. But there are always edge cases. If you have an edge case, then this library might be for you.
My edge case at the time was redirecting users to a completely separate mobile site. I tried to keep this script small (currently ~1.3k bytes, minified) and simple, because it would need to execute in the <head>, which is generally a bad idea, since JS blocks the downloading and rendering of all assets while it parses and executes. In the case of mobile redirection, I don't mind so much, because I want to start the redirect as soon as possible, before the device has a chance to start downloading and rendering other stuff. For non-mobile platforms, the script should execute fast, so the browser can quickly get back to downloading and rendering.
How it works in the browser
isMobile runs quickly during initial page load to detect mobile devices; it then creates a JavaScript object with the results.
In NodeJS
You might want to use this library to do server-side device detection to minimize the amount of bytes you send back to visitors. Or you have your own arbitrary use case.
How is works in NodeJS
You import and call the isMobile function, passing it a user agent string; it then returns a JavaScript object with the results.
Devices detected by isMobile
In a browser, the following properties of the global isMobile object will either be true or false. In Node, isMobile will be whatever you named the variable.
Apple devices
isMobile.apple.phoneisMobile.apple.ipodisMobile.apple.tabletisMobile.apple.device(any mobile Apple device)
Android devices
isMobile.android.phoneisMobile.android.tabletisMobile.android.device(any mobile Android device; OkHttp user agents will match this)
Amazon Silk devices (also passes Android checks)
isMobile.amazon.phoneisMobile.amazon.tabletisMobile.amazon.device(any mobile Amazon Silk device)
Windows devices
isMobile.windows.phoneisMobile.windows.tabletisMobile.windows.device(any mobile Windows device)
"Other" devices
isMobile.other.blackberry_10isMobile.other.blackberryisMobile.other.opera(Opera Mini)isMobile.other.firefoxisMobile.other.chromeisMobile.other.device(any "Other" device)
Aggregate Groupings
isMobile.any- any device matchedisMobile.phone- any device in the 'phone' groups aboveisMobile.tablet- any device in the 'tablet' groups above
Usage
Node.js
Install
yarn add ismobilejs
Use
import isMobile from 'ismobilejs';
const userAgent = req.headers['user-agent'];
console.log(isMobile(userAgent).any);
Browser
A real-word example: I include the minified version of the script, inline, and at the top of the <head>. Cellular connections tend to suck, so it would be wasteful overhead to open another connection, just to download ~1.3kb of JS:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8" />
<script>
// Minified version of isMobile included in the HTML since it's small
(function () {var f=/iPhone/i,j=/iPod/i,p=/iPad/i,g=/\bAndroid(?:.+)Mobile\b/i,i=/Android/i,d=/\bAndroid(?:.+)SD4930UR\b/i,e=/\bAndroid(?:.+)(?:KF[A-Z]{2,4})\b/i,c=/Windows Phone/i,h=/\bWindows(?:.+)ARM\b/i,k=/BlackBerry/i,l=/BB10/i,m=/Opera Mini/i,n=/\b(CriOS, Chrome)(?:.+)Mobile/i,o=/Mobile(?:.+)Firefox\b/i;function b($,a){return $.test(a)}function a($){var a=($=$, ("undefined"!=typeof navigator?navigator.userAgent:"")).split("[FBAN");void 0!==a[1]&&($=a[0]),void 0!==(a=$.split("Twitter"))[1]&&($=a[0]);var r={apple:{phone:b(f,$)&&!b(c,$),ipod:b(j,$),tablet:!b(f,$)&&b(p,$)&&!b(c,$),device:(b(f,$), b(j,$), b(p,$))&&!b(c,$)},amazon:{phone:b(d,$),tablet:!b(d,$)&&b(e,$),device:b(d,$), b(e,$)},android:{phone:!b(c,$)&&b(d,$), !b(c,$)&&b(g,$),tablet:!b(c,$)&&!b(d,$)&&!b(g,$)&&(b(e,$), b(i,$)),device:!b(c,$)&&(b(d,$), b(e,$), b(g,$), b(i,$)), b(/\bokhttp\b/i,$)},windows:{phone:b(c,$),tablet:b(h,$),device:b(c,$), b(h,$)},other:{blackberry:b(k,$),blackberry10:b(l,$),opera:b(m,$),firefox:b(o,$),chrome:b(n,$),device:b(k,$), b(l,$), b(m,$), b(o,$), b(n,$)},any:!1,phone:!1,tablet:!1};return r.any=r.apple.device, r.android.device, r.windows.device, r.other.device,r.phone=r.apple.phone, r.android.phone, r.windows.phone,r.tablet=r.apple.tablet, r.android.tablet, r.windows.tablet,r}window.isMobile=a();})();
// My own arbitrary use of isMobile, as an example
(function() {
var MOBILE_SITE = '/mobile/index.html', // site to redirect to
NO_REDIRECT = 'noredirect'; // cookie to prevent redirect
// I only want to redirect iPhones, Android phones
if (isMobile.apple.phone, isMobile.android.phone) {
// Only redirect if the user didn't previously choose
// to explicitly view the full site. This is validated
// by checking if a "noredirect" cookie exists
if (document.cookie.indexOf(NO_REDIRECT) === -1) {
document.location = MOBILE_SITE;
}
}
})();
</script>
</head>
<body>
<!-- imagine lots of html and content -->
</body>
</html>
jsDelivr CDN 
Alternatively, you can include this library via jsDelivr CDN in a script tag:
<script src="https://cdn.jsdelivr.net/npm/ismobilejs@1/dist/isMobile.min.js"></script>
Visit the isMobile jsDelivr page to get the most up-to-date URL pointing to the lastest version.
Building manually
After checking out the repo, install dependencies:
yarn install
Then build the library:
yarn build
Three versions of the library will be generated:
./cjs/index.js- the CommonJS version of the library./esm/index.js- the ESModule version of the library./dist/isMobile.min.js- the browser version of the library
Additionally, types will be output to types.
Contributing
This library uses Spotify's web-scripts project to build, lint, test, format and release the this library.
You must use yarn commit rather than git commit to commit files. This enforced commit messages to following a specific format and enables automation of release notes and version bump.