Tommy Lahitte | Debug Vault
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Speed Up Builds with Unreal Build Accelerator (UBA)

UBA distributes compilation tasks across a Horde cluster, dramatically reducing full rebuild times. Enabling it is a single XML config change, no code modifications required.

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Unreal Build Accelerator (UBA) offloads C++ compilation to a Horde cluster. For large projects, it can cut full rebuild times from hours to minutes by parallelizing across many remote machines.

Enable UBA

Create or edit the BuildConfiguration.xml file at this path:

bash
%APPDATA%\Unreal Engine\UnrealBuildTool\BuildConfiguration.xml
xml
<?xml version="1.0" encoding="utf-8" ?>
<Configuration xmlns="https://www.unrealengine.com/BuildConfiguration">
  <BuildConfiguration>
    <bAllowUBAExecutor>true</bAllowUBAExecutor>
  </BuildConfiguration>
  <Horde>
    <Server>https://horde.devtools.epicgames.com</Server>
    <ConnectionMode>relay</ConnectionMode>
    <Cluster>_auto</Cluster>
  </Horde>
</Configuration>
You must have access to a Horde server and be on the correct network/VPN for the remote execution to work. Local compilation still works if the cluster is unreachable.

How It Works

  • UBA intercepts UnrealBuildTool compile jobs and dispatches them to idle Horde agents
  • The relay connection mode routes traffic through the Horde server (no direct agent access needed)
  • _auto cluster selection picks the best available cluster automatically
  • Falls back to local compilation transparently if the cluster is unavailable

Verifying It Is Working

Start a build and watch the UnrealBuildTool output. You should see lines indicating remote compilation tasks being dispatched. The total compile time will be significantly lower than local-only.