We will be removing the possibility to create an "old” world in Bedrock with the 1.18 release. The ‘old world type’ was originally the only world type available in Bedrock Edition (formerly known as Pocket Edition) but we later added ‘infinite and ‘flat worlds’ as well.
Today, the majority of players are playing infinite and flat worlds, which is why we want to focus even more on maintaining and improving the quality of those world types.
What is an old world type?
An old world is a finite world type that measures 256 x 256 blocks horizontally, and a maximum height of 128 blocks.
What will happen to my existing ”old” world type worlds?
Your existing worlds will continue to work and you will still be able to convert them to infinite worlds as before.
Will my old world type get the new world height with the 1.18 release?
No. The world generation and world height will not change in existing old world type worlds.
I don’t want an infinite world. How do I limit my world, similar to how I could limit worlds with the old world type?
After the 1.18 release creating Old limited worlds won’t be possible, but Old type worlds created beforehand will continue to work. Players who would still like to limit their worlds can still do so using Border blocks. These can be used by enabling cheats and entering the command /give @p border_block.