Hi. I would like to build mob grinder on version 1.12.2 on vanilla server but I dont know how like... I know how to build the structure but I dont know where since I´ve heard that it can not be in range with spawner or what and I just dont understand it If someone would take a minute and explain it to me I would highly appreciate him. Thanks.
Hi, there's nowhere in particular they have to be, but for a reasonable spawn rate you should make sure there are as few places where mobs can spawn outside the spawner within 128 blocks of where you (and other players) will be when you are using it as possible.
The easiest way is to build it up above the world, for instance 128 blocks up over the ocean or plains.
Otherwise you can spend loads of time lighting up or slabbing caves, and the surface if you want it to work well during the day.
Unfortunately, on a server, you usually have no control over where other players are and how many mobs are spawning around them, mostly you have to just take your chances, unless you can find a time when the server is mostly empty.
People who want the very highest spawn rates possible build it as low down as possible and dig away everything else in the chunk(s) it is in but I think that's overkill.