For those using the browser-based , "Library" typically refers to the 3D Warehouse , an immense online repository where you can find and download millions of pre-made 3D models. While SketchUp Free has some limitations—such as not supporting external plugins or extensions—it provides several ways to manage and access content libraries directly. Core Libraries in SketchUp Free
A built-in "Browse" menu that contains standard textures like wood, glass, and stone to apply to your designs. How to Use and Manage Your Library
The primary library for users. It is an open, searchable gallery of millions of free models, ranging from furniture to entire buildings, uploaded by both individual users and real-world brands.
Accessible directly within the SketchUp Free interface, this panel allows you to search the 3D Warehouse and immediately place objects into your active model.