Is it even possible to do this in 2025? Thinking about running some old published adventure modules, but I have a couple of players whom I suspect will run to the internet and peek at things only the GM should know. Other than re-writing the adventure myself, can I even guard against this?
I homebrew everything these days, but back when I ran off-the-shelf adventures, I customized and arranged large parts of them as well. I didn’t do it to catch cheaters, but it would be very good for that.
Anyway, I just told players not to read outside sources and be careful about what you search for. I said if you come across outside information once, I’ll chalk it up to an accident, but if it happens repeatedly, I’ll remove you from the group. I didn’t feel the need to explain or justify that.
I had one case of someone searching a name to figure out the spelling, and they ended up spoiling themselves for a major character reveal. They were a good player and they regretted spoiling it for them themselves, and it never happened again.