How to Verify the Presence of a Chrome Extension Using an External Script?

Verify the Presence of a Chrome Extension Using External Script

In developing Chrome extensions, integrating them with external JavaScript scripts to detect their installation status is essential. This allows you to tailor the user experience based on whether the extension is present on their browser.

Fortunately, Chrome provides a mechanism for exchanging messages between the webpage and the extension. To achieve this, follow these steps:

1. Extend the Chrome Extension:

   • In the background.js file, handle external messages with 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. Communicate from the Webpage:

   • Utilize the following code from the webpage:

   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. Handle Permissions:

   • In manifest.json, specify the domains that can connect to your extension:

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

4. Exception Handling (2021 Update):

   • To handle exceptions when the extension is not installed or disabled, add a check for runtime.lastError:

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

By implementing these steps, you can seamlessly detect the presence of your Chrome extension using an external JavaScript script and adjust the user experience accordingly.

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