If you are looking to expand your library significantly, these methods are more efficient:
You cannot add the entire Steam library to a single cart at once.
Buying every item on Steam is a massive undertaking that currently costs . While there is no official "buy all" button, you can track the total price and manage large purchases through specific community tools and Steam features. Total Cost to Buy Everything buy all of steam
For individual games with many add-ons, use the "Add all to cart" button found on the game’s store page.
Developers often create Steam Bundles that allow you to buy entire franchises or publisher catalogs at a set discount. Mass activate free Steam Games | SteamDB Free Packages tool If you are looking to expand your library
If you use external keys to add games, Steam typically limits activations to about 50 per hour .
Steam Support generally does not offer a "buy all" package for standard consumers. Total Cost to Buy Everything For individual games
Note that Steam’s terms of service clarify you are purchasing a license to play games, not permanent ownership of the software itself. How to Manage Large-Scale Acquisitions