The spawn chunks are the 16x16 (or 12x12 without calculating the lazy chunks) chunks around the world spawn point. These spawn chunks are specials from the others, because they are always loaded, if a player is in the overworld.
- If there is at least 1 passive animal in the spawn chunks, the animal spawning will be disabled, and you will be able to get animals only in newly generated terrain (because animals come with new terrain as well as they spawn on their own)
- If you send an entity throught an end portal, or jump into it without having a bed set, you will be at the world spawn location. This is inside the spawn chunks, and the spawn chunks are located around it.
- The outer side of the spawn chunks can turn into lazy chunks meaning that you only have 12x12 area of chunks in the spawn chunks that are fully loaded always. The 2 chunk border of the spawn chunks are lazy chunks, meaning that they don't process entities. If a player is in distance, they will of course turn into fully loaded chunks.
- There is a rare chance to find 18x18 spawn chunks. Video
- Fun fact: If you newly spawn in a world, and teleport to unloaded chunks near the spawn chunks, you will see the spawn chunks as the terrain you are in is generating.
Loading and unloading spawn chunks with portalsEdit
The spawn chunks are only loaded if at least one player is in the overworld. If all players are in another dimension (the nether or the end), the spawn chunks will unload after 15 seconds (60 before 1.9). To prevent this, you can send items through a portal every 5 seconds (to prevent lag unloading the chunks), because if an entity goes to the overworld, it will load the spawn chunks for 10 seconds. (In 1.8 this was 60 seconds, and we used to send items through every 45 seconds, but in 1.9 the timing has changed.) If it isn't a player, the spawn chunks will unload. That is the reason it is necessary to send items over and over. This would work with other entities as well.
Finding the spawn chunksEdit
Method 1 - Maths - Video
'Method 2 - Items - 'Video
Method 3 - Internal programs (might be cheaty)