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Documentation Index

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Onyx is a desktop application that puts a graphical interface on top of Steamworks’ SteamCMD upload tooling. Instead of manually invoking steamcmd.exe with long argument strings for each app, Onyx lets you manage accounts, configure apps and depots, and run multiple uploads in a single session — all from one window.

What Onyx does

Onyx wraps the official Steamworks ContentBuilder workflow. It reads and writes the same .vdf configuration files that Valve’s own tools use, so everything you do in Onyx is compatible with your existing Steamworks setup.

Multi-app uploads

Queue and run uploads for multiple Steam apps and depots in one session without switching between terminal windows.

VDF config management

Generate, view, and edit app_<APPID>.vdf and depot_<DEPOTID>.vdf build config files directly inside the app.

Steam account management

Store and switch between multiple Steam accounts. Onyx passes credentials directly to SteamCMD at upload time.

Real-time console output

Watch live SteamCMD output as each build uploads. Steam Guard prompts are detected and surfaced automatically.

Upload cancellation

Cancel an in-progress upload at any time without needing to kill a background process manually.

Windows and Linux

Distributed as a single executable for Windows (.exe) and Linux (.x86_64). No installer or runtime required.

How it fits into the Steamworks workflow

Onyx sits between your local build output and the Steam backend. It does not replace the Steamworks SDK or SteamCMD — it orchestrates them. The standard flow looks like this:
  1. You build your game and place files in the ContentBuilder content/ directory.
  2. Onyx generates or reads the app_*.vdf and depot_*.vdf configs in the scripts/ directory.
  3. Onyx calls steamcmd.exe (Windows) or steamcmd.sh (Linux) with the correct arguments.
  4. SteamCMD uploads the build and writes logs to the output/ directory.
Onyx handles steps 2–3 and surfaces the output from step 4 in real time.

Who Onyx is for

Onyx is useful for any developer or team that publishes to Steam and wants to avoid scripting or manual command-line work for every release. It is especially helpful when managing multiple depots (for example, separate depots per platform or DLC) or when multiple team members need to trigger uploads with their own Steam credentials.
Onyx requires an existing Steamworks ContentBuilder installation. If you do not have the Steamworks SDK set up yet, start with the installation guide before continuing.

Next steps

Quickstart

Go from zero to your first upload in a few steps.

Installation

Detailed setup instructions for Windows and Linux.

Setting up ContentBuilder

Configure your Steamworks ContentBuilder directory for use with Onyx.

Uploading builds

Learn how to queue and run uploads for your apps and depots.

Build docs developers (and LLMs) love