The minimum recommended RAM for running a Minecraft server used to be 2 GB. With the addition of new biomes, mobs, and other features along the way, however, this has increased to 4 GB or more for a server with a moderate number of players.
This is especially true for newer versions of Minecraft, such as 1.16 and later, which have added even more content and features with larger-scale moves like the Nether update, Caves and Cliffs update, The Wild update, and more.
For larger servers with many players and a large world, the recommended RAM can now be 8 GB or more, depending on the size and complexity of the server. Beyond this, modded Minecraft servers typically require even more RAM than vanilla servers.
This is because mods can entirely redesign or introduce massive features to the game, which can significantly increase the memory usage of the server. As a result, modded Minecraft servers often require at least 8 GB or more of RAM, with some reaching 16 GB and beyond.
This steady growth is made all the more complicated by Minecraft’s optimization issues when it comes to multi-thread performance, though this has been improved over time by mod and plugin developers.