[adityakothadiya]

Actually you can use Mixpanel exactly for that. We're a B2B company and have exact same use case as yours. We provide some Javascript code that our customers add on their sites. We don't require our customers to have Mixpanel account and we also don't load our Mixpanel JS to our customers' site.

What we do is - we send requests to our server from our customers' site with key information that we want to track, and then we send those events to Mixpanel through server API (e.g. PHP) calls.

It works really well for us. We're measuring how our customers' customers are using our Javascript based widget, and are able to improve our performance, engagement, etc.

Hope this helps.