Can Websites Detect If a Chrome Extension is Installed?

How to Detect Chrome Extension Installation from External Script

In order to create a seamless user experience, it is often necessary to determine if a user has a specific Chrome extension installed. This allows websites to adapt their content and functionality based on the presence of the extension.

According to the latest updates, Chrome now provides the ability to send messages from a website to an extension. To achieve this, follow these steps:

1. In the extension's background.js file, add the following code:

   chrome.runtime.onMessageExternal.addListener(
       function(request, sender, sendResponse) {
           if (request) {
               if (request.message) {
                   if (request.message == "version") {
                       sendResponse({version: 1.0});
                   }
               }
           }
           return true;
       });

2. From the website, you can send a message to the extension:

   var hasExtension = false;
   
   chrome.runtime.sendMessage(extensionId, { message: "version" },
       function (reply) {
           if (reply) {
               if (reply.version) {
                   if (reply.version >= requiredVersion) {
                       hasExtension = true;
                   }
               }
           } else {
               hasExtension = false;
           }
       });

3. Once the extension responds, you can check the hasExtension variable to determine the user's installation status.

Note that the message exchange is asynchronous, so you may need to implement logic to handle the potential for delay.

Edit:

1. Add an entry to the manifest.json file specifying the domains that are allowed to send messages to the extension:

   "externally_connectable": {
       "matches": ["*://localhost/*", "*://your.domain.com/*"]
   },

2. In the callback of chrome.runtime.sendMessage, handle the potential error that may arise if the extension is not installed or is disabled:

   if (chrome.runtime.lastError) {
       // handle error 
   }

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