Quote from: bitcoin talk on Today at 02:56:52 AM

What tools do gambling or classifieds sites use to detect or know your using a vpn?

The easiest way to do it, comparing against other IPs known to be owned by VPN companies, one example here
https://ipinfo.io/tools/vpn-providers-detected
There are services online that provide updated information on those, a bit pricy but with thousands of IPs, so unless you're using your own private one sooner or later it will get tracked.
But there are also other methods, most of them rely on leaks from your browser, webRTC, info on your timezone, and others, so normally before browsing you should test your browser for information leaks.

Quote from: Orpichukwu on Today at 03:02:21 AM

I don't know if there are any special tools they use, but to me, it's very easy to know who is using VPN in some cases. If you notice a particular user who, each time they login to their account, appears in a new location with a different IP address from their last login, is that not an obvious sign of VPN usage?

What if I'm using the same IP or the same range from the same country?