How to use the web page to determine whether the software is installed on the user's machine

How to use the web page to determine whether the software is installed on the user's machine? we have developed a small software for the website. it has its own information chat function, including reading website information. I would like to ask how to use the web page to determine whether the software is installed on the user's machine? If the software is installed, you can start the sending information window of the software. if not, go to the download and installation page and use the webpage to determine whether the software is installed on your machine.
We have developed a small software for our website. it has its own information chat function, including reading website information.
I would like to ask how to use the web page to determine whether the software is installed on the user's machine? If the installation is complete, you can start the sending information window of the software. if not, go to the download and installation page.

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I have also asked such questions.

Someone told me this is illegal .. -_-!!!

Then I asked the manager. Because we were doing this.

The manager told me this is the plug-in provided by the software party when installing the software.

ActiveX plug-in.

Then, you can use the JS code on the webpage to determine whether the plug-in has been installed.

In this way, you can determine whether your computer has installed the software you want .. Well ..
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Php cannot.