Valheim patch 1.0.15 fixes a terrain duplication problem that could reduce performance in affected worlds. Iron Gate released the follow-up on September 18 after identifying the issue in the previous build.

What the patch fixes

A Valheim settlement and terrain
The patch addresses duplicated terrain data rather than changing normal world generation.Iron Gate / Steam

The bug could leave overlapping terrain in a world and increase the work required to render or process an area. Patch 1.0.15 prevents that duplication and is the update players should install before continuing on the affected version.

What affected players should do

Iron Gate's official notes include recovery guidance for worlds that still show the problem. Back up the world before using any repair step, confirm the game is on 1.0.15, and use the developer's instructions rather than deleting world files manually.

Players exploring a Valheim biome
Back up an affected world before following the official recovery steps.Iron Gate / Steam

This is a narrow repair patch, not a content update. Install it because it protects an existing world and performance, then return to the larger 1.0 changes once the save behaves normally.