After tests and investigations, unfortunately, we cannot offer the possibility to access the Apex Sneak Preview via the Game Updater tool. However, there is a solution to have access to both builds, main branch and Sneak Preview. The trick is to use Game Updater to maintain the main branch of the game and Steam for the development branch. Note that we don't recommend this method for regular users as it involves some potentially risky steps for your game installation. In order to lessen the amount of data to download, here some steps: Note: Folder names and paths depend on your Steam installation and folder structure. Preparing the main branch Go into the parent directory of your Arma 3 game (...\steamapps\common) Duplicate the folder Arma 3 (copy and paste should be enough) and rename it into Arma 3 [Main] Run Game Updater, and relocate the install directory to the new one. Open the Options form and be sure to have "Check local content (validation)" set to "Yes". Once back on the main form, click "UPDATE" and wait for the verification of the cache. Preparing the development branch Go into your Steam Library, category game, right click on Arma 3 and then Properties. From here, select the Apex Sneak Preview Build Or type the password of the RC branch and select it (they are the same) Wait for the Steam to download the branch  :292: