Is it possible to somehow prohibit the indexing of a domain and all its subdomains at once?

Question

Google

I have a habit of storing client sites on my demo server.
And it’s more convenient to show, and it’s always necessary for development.
But recently I noticed that all sites were indexed.
And some also knocked out real sites from the search)))
The question is, is it possible to somehow completely prohibit indexing a certain domain?
Along with subdomains.
I know robots, but you need to put it in a folder all the time.
And this can be forgotten, or then not removed from the client's site.
So, is there another solution?

Answer 1

If the site is on wordpress, then you can disable indexing from the admin panel .