Phantom’s browser extension and mobile in-app browser will both inject a phantom object into the window of any web application the user visits, provided that site is using https://, on localhost, or is 127.0.0.1. Phantom will not inject the provider into iframes or sites using http://. If a phantom object exists, Bitcoin and Ordinals dapps can interact with Phantom via the API found at window.phantom.bitcoin. To detect if Phantom is installed, an application should check for an additional isPhantom flag like so: 
const isPhantomInstalled = window?.phantom?.bitcoin?.isPhantom
If Phantom is not installed, we recommend you redirect your users to our website https://phantom.com/. Altogether, this may look like the following: 
const getProvider = () => {
  if ('phantom' in window) {
    const anyWindow: any = window;
    const provider = anyWindow.phantom?.bitcoin;
   
    if (provider && provider.isPhantom) {
      return provider;
    }
  }

  window.open('https://phantom.com/', '_blank');
};
When adding a Phantom button to your dapp’s wallet modal, we recommend using the name “Phantom” with an SVG/PNG icon, which you can find in Logos and assets. An example Phantom button in a wallet modal