A live subscriber counter is cool for a stream or page. And you can make it free. Let's cover a few ways, from simplest to flexible.
There are free sites showing a counter by channel name, like those giving a subscriber counter widget. You enter your channel, get a link and paste it into OBS as a Browser Source. Simplest path, no code.
A more flexible option is the official YouTube API. It's free: in Google Cloud Console you create a project, enable YouTube Data API, get a free key. You paste the key into a widget and it shows your channel's exact data. The free API limit is plenty for a counter.
Go to console.cloud.google.com, create a project. In the API library find YouTube Data API v3 and enable it. In Credentials create an API key. This key is what goes into the counter widget. Never show the key publicly.
The ready counter widget adds to OBS (Browser Source) for a stream or to a card page. Updates automatically, showing the current subscriber number in real time.
Default free counters look plain. We'll make you a stylish animated counter in your colors, for a stream or page. You insert your own free key, we have no access to your account. Write to us for examples.