Tectonic

Tectonic is a world-generation mod created by Apollo. A terrain overhaul mod that generates dramatically larger mountains, deeper valleys, and more varied continent-scale landforms. As a world gen mod it concentrates on terrain, biomes, and the shape of the world itself, and it has been downloaded around 15 million times, which puts it among the options players reach for in this space.

Tectonic is built for players who want bigger, more mountainous terrain without a heavy block overhaul. It reshapes Minecraft's terrain noise so mountains tower higher, valleys cut deeper, and coastlines feel continent-scale, all on top of vanilla biomes. 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 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.

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

Tectonic only changes world-generation shaping, so it adds essentially no ongoing tick cost once chunks are generated.

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