Javascript to check if PWA or Mobile Web

I was curious if anyone knew a javascript based method for detecting whether the web experience was being run as a PWA (progressive web app) or it was simply being run as a standard mobile website (with full browser UI).

Is there any difference between a PWA that is "installed" versus one that isn't but still has the service worker and/or app cache registered?

If this is for analytical purposes you could set the start URL in the manifest file to include a query string parameter, ex:

"start_url": "./?mode=standalone"

Then in your JavaScript you are able to check for this query string parameter.

Updated (2020-08-19)

Pete LePage wrote a blog on how to setup a custom dimension in Google Analytics using the code below which checks the display mode using window.matchMedia:

let displayMode = 'browser';
  const mqStandAlone = '(display-mode: standalone)';
  if (navigator.standalone || window.matchMedia(mqStandAlone).matches) {
    displayMode = 'standalone';
  }
ga('set', 'dimension1', displayMode);

Read more: https://petelepage.com/blog/2020/08/measure-understand-how-installed-pwa-users-differ-from-browser-tab-users/

Updated (2017-01-20):

Alternatively you could check in JavaScript using:

if (window.matchMedia('(display-mode: standalone)').matches) {
  console.log("This is running as standalone.");
}

Edit 11 Oct 2019: Added an extra switch to check if the app is launched via TWA - document.referrer.includes('android-app://')

This works for all - TWA, Chrome & Safari:

const isInStandaloneMode = () =>
      (window.matchMedia('(display-mode: standalone)').matches) || (window.navigator.standalone) || document.referrer.includes('android-app://');

 if (isInStandaloneMode()) {
    console.log("webapp is installed")
}

if (window.matchMedia('(display-mode: standalone)').matches) {
  console.log("This is running as standalone.");
}

This answer is correct but it's worth to mention that PWA could run on plenty of display modes:

• fullscreen
• standalone
• minimal-ui
• browser

If you run your PWA in a 'fullscreen' mode it will return false so additional checks are necessary like:

function isPwa() {
    return ["fullscreen", "standalone", "minimal-ui"].some(
        (displayMode) => window.matchMedia('(display-mode: ' + displayMode + ')').matches
    );
}

Note that window.matchMedia check will return true for the 'browser' display mode even when it's not an installed PWA app.

Progressive enhancement is more a concept than an specific function or method that involves several technologies. Now progressive web apps are base on service workers which you can verify if the browser support it.

// Check for browser support of service worker
if ('serviceWorker' in navigator)

Project lighthouse can help you to detect whether an application is progressive enhanced by performing evaluations of several technologies. Take a look on it.

Hope this help, to clarify.

In my PWA, created with Microsoft Visual Studio 2017, following statement works:

var isPWA = navigator.userAgent.match(/MSAppHost/i);