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?
Counter question, does it matter? If they have fun by knowing what’s coming and being able to prepare for it does that make the experience worse for other players or yourself? If not then who cares let them have at it.
If yes then you need to address it somehow, the usual answer to these sorts of things is to just have an adult conversation with the players about expectations.
If you know your players and that won’t work then you have some choices to make, again do you care enough to put in more work on top of already running the game?
If it’s going to be an issue and they will abuse access to the module even after you’ve asked them not to, do you really want to play with them?
If the answer is still yes then I suggest altering things slightly so them having pre knowledge doesn’t help, locations of key stuff, attitudes of NPCs, stat blocks/ monsters and enemy placement could all be changed pretty easily with fairly little work, I’d definitely rework the monsters at least, I wouldn’t go as far as traps designed to catch them out though that’s punishing the party for a player.