Detecting a browser addon using JavaScript or C#?

Question

We are writing a website in C#, and we need to detect if the client's browser has a certain (custom developed) add-on installed.

We have figured out a way how to do it when the client is using Firefox or Internet Explorer. How can we do the same with Safari and Chrome?

Answer 1

Since addons have permission to modify DOM
using the add-on you can inject some javascript variable(eg var IsMyAddonNameInstalled = 'true' ) into the DOM when your website is requested from browser
and then pass it to server using AJAX request or hidden input field .

PS: This will work on all browsers

Answer 2

You can add your Addon name to User-Agent variable of your browser (by modyfing this value in browser settings store, open about:config in URL for Firefox). Then you can read it back from Request object.