3D WebView for Windows and macOS embeds the Chromium browser engine, which adds about 170 MB to the size of an app. 3D WebView uses Chromium Embedded Framework (CEF) to embed Chromium, and CEF considers some components optional. This page from CEF describes which files are required and which are optional. So, if achieving the smallest possible size is important for your application, you can try removing the optional components it lists. However, as the page notes, removing some of the optional components may impact its functionality.