It might have used the Netscape Plugin Application Programming Interface (NPAPI) https://en.wikipedia.org/wiki/NPAPI https://en.wikipedia.org/wiki/NPAPI. Howev

It might have used the Netscape Plugin Application Programming Interface (NPAPI) https://en.wikipedia.org/wiki/NPAPI https://en.wikipedia.org/wiki/NPAPI. However it would have involved a step of downloading and installing a plugin, a few extra clicks.