Terralith

Terralith is a world-generation mod created by Starmute. A vanilla-style biome overhaul using only vanilla blocks, adding dramatic terrain features and over 85 new biomes. As a world gen mod it concentrates on terrain, biomes, and the shape of the world itself, and it has been downloaded around 40 million times, which puts it among the options players reach for in this space.

Terralith is built for players who want dramatic vanilla-plus terrain with no new blocks to learn. Built on Minecraft's own noise system, it overhauls the Overworld with new biomes and landforms while staying fully data-driven and lightweight. It is approachable enough to drop into a world and use right away, with little setup required.

The mod is available for Forge, Fabric, NeoForge, and Quilt, so it fits a range of modpacks and launchers. It currently supports Minecraft 1.20.1, 1.20.4, and 1.21.1, spanning the 1.20.1 to 1.21.1 releases. It runs on both the client and the server, so on a multiplayer server every player who connects needs it installed alongside the server itself.

Terralith works particularly well alongside Tectonic, Biomes O' Plenty, and Nature's Compass. Because it ships for both Fabric and Forge-family loaders, it slots into most popular modpacks regardless of which side they are built on.

Because it is data-driven and adds no entities or block ticks, Terralith has a negligible runtime cost beyond normal world generation.

If you are comparing options, similar mods include William Wythers' Overhauled Overworld and Tectonic. They cover comparable ground, so the right choice usually comes down to your loader, version, and the rest of your pack.