Minecraft wiki entry for The_Nether, associated text: Bedrock comprises the top (including and below layer 127) and bottom 4 layers in a rough pattern, essentially making the Nether 128 blocks high unlike the Overworld's 320. In the infinite worlds of the Java and Bedrock Editions, the Nether is also horizontally infinite. In Bedrock Edition, the build limit in the Nether is 128 blocks, despite it being 256 in all other dimensions.