Tutorial:Chunk ban
Use at your own risk.
Chunk banning is making a chunk or area have too much data for servers to send to the client, resulting in repeated Java exceptions that disconnect users from the server that are too close. It is called a "ban" as the repeated Java exceptions prevent players from connecting to the server.
There are two methods of chunk banning; the first is the method of building high NBT structures, although this does not work in recent versions. The second (and more reliable) chunk banning method, now known as area banning, is to fill a shulker box with high NBT books and drop it as an item entity. Unlike chunk banning, this will kick you from the game if you are within a 32 block radius blocks of the dropped item on a Vanilla server (This value will change with render distance), or 32 blocks on a server with Spigot server software. In addition, if any entity such as a Fox or a Zombified Piglin holds a Shulker Box with high NBT books the range on a Spigot server the ban range will be 48 blocks however it will return to 32 if the user has the minimum render distance
Area banning is not functional on Paper and Purpur server software, but works on vanilla servers and modded ones, such as Fabric.
Chunk bans are mainly used in prisons and also feature use in anarchy servers, and safe houses to keep people out of certain places. The first reference of a chunk ban was the furnace chunk ban in 2b2t, and the first non-anarchy reference was in a prison called The Obelisk by Miningblob. Ever since then all serious prisons as well as safe houses have been made with dropped shulker box item bans, most notably Gaia's Vault by TheDeafCreeper+SeenSven and Wifies' safe house.
There is a lot of misinformation about the difference between Chunk bans and Area bans; so watch this informative video by Jerrylum to fully understand Area Banning.
When in range of a area ban a player is still able to perform a few actions, due to players having a brief window of about a few ticks before the server kicks them from the game, this is called banned inputs
DO NOT hold it in your inventory if playing on 1.18.1 or higher. this will ban the player whenever they re-join the server in a method called inventory banning. The solutions are either to change the nbt data in the server/world file to remove the shulker box or to have a friend place a repeating command block with "/clear @p shulker_box" near you and then try to join, or if it is in a survival server a hole can be cleared going down into the void, and having the player fall into the void using banned inputs where they can die.
All area bans made before 1.21 will no longer work in 1.21, this is because the maximum packet size has been increased. Area bans can still be made post 1.21: this is done by adding more books to the shulker box using bundles, or by writing books that contain much more data displayed in this video by Avatardotpng, this style is called compression banning.
There is a special type of area ban called a ZPI (Zone Protection Item), this ban works by containing a precise amount of data so that if loaded it will not be a sufficient amount of data for a kick, however if placed into an item frame it will then be over the packet data size limit, this creates a special behaviour, where all places in the vicinity are still able to remain on the server however if new players load this area they are sent the packet for both the ZPI and the item frame which will kick them from the game, this type of ban was discovered by JerryLum
additionally post 1.21 a ZPI can be active in a players inventory, if a player holds the ZPI in their hand it will be act as a normal ZPI (they may also have to hold an item with multiple enchantments in the other hand), however this is a very risky thing to do as by doing many actions (opening the inventory, equipping armour, using fireworks) the player will get kicked themselves and become inventory banned
If an area ban item is placed inside of a decorated pot it creates a special type of area ban called a pot ban that bans a 7*7 chunk area (this is based on the clients render distance) centred around the chunk that contains the pot, this will act as a ZPI
As area banning works by having the server send oversized packets to users, any method of preventing packets from being sent to a client will prevent being kicked, the most common and most practical way to do this is by entering null state (this can be done by right clicking on a windowed instance of minecraft)
