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Onyx is a free, open-source desktop application that streamlines your Steam build publishing workflow. Instead of running SteamCMD commands manually or using Valve’s official GUI one app at a time, Onyx lets you queue multiple apps and depots, set build descriptions, and upload them all in a single session — with real-time console output and Steam Guard detection built in.

Quick Start

Go from download to your first successful Steam upload in minutes.

Installation

Download Onyx for Windows or Linux and get it running alongside your Steamworks SDK.

Set Up ContentBuilder

Point Onyx to your Steamworks ContentBuilder directory and create your VDF configs.

Uploading Builds

Select apps, set descriptions, and upload multiple builds with one click.

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What Onyx does

Onyx wraps SteamCMD in a clean, purpose-built GUI that mirrors the structure of Valve’s official Steamworks tools. It reads your existing VDF build scripts, lets you manage them visually, and drives SteamCMD in the background to perform the actual upload.

Batch uploads

Upload multiple apps and their depots in a single session without re-entering credentials each time.

VDF management

Generate and edit app_*.vdf and depot_*.vdf build configuration files from within the app.

User accounts

Store multiple Steam accounts and switch the active uploader account without retyping credentials.

Live console

Watch SteamCMD output in real time, with automatic detection when Steam Guard input is needed.

Cross-platform

Runs on Windows and Linux, invoking the correct SteamCMD binary for each platform automatically.

Cancel anytime

Stop an in-progress upload at any time without losing your selected app queue.

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How it works

1

Point to your ContentBuilder folder

Open the Setup dialog and browse to your Steamworks SDK ContentBuilder directory. Onyx validates that the content, output, and scripts subdirectories are present.
2

Create or load your app configs

Onyx reads app_*.vdf files from the scripts/ folder. You can also create new app and depot VDF files from scratch inside the app.
3

Select a Steam account

Add your Steam username and password in the Users panel, then select which account to use for this upload session.
4

Upload

Check the apps you want to upload, optionally set a build description, and click Upload. Onyx runs SteamCMD for each app in sequence and streams the output to the console panel.
Onyx is a local desktop tool — it never sends your credentials to any external server. All authentication happens directly between SteamCMD and Valve’s servers on your machine.