A progress bar appeared. Spine-3.8.99-windows-setup.exe . File size: 74MB. It matched the usual size of the launcher.

Are you looking to to 3.8, or are you setting up a new pipeline from scratch?

: Spine will automatically download the required files and restart in the 3.8.99 environment. Legacy Support vs. Modern Features

You cannot. Spine is not backwards compatible . A file saved in 4.0 uses a different JSON schema and physics data. If you need to work in 3.8.99, you must keep all source files saved in the 3.8 format. Consider using a version control system (Git) with separate branches for legacy work.

While 3.8.99 is a "safe" version for many developers, Esoteric Software recommends upgrading to the latest 4.2+ builds for newer features like , the improved graph editor, and significantly faster performance. You can compare features and check for the latest updates on the official Spine Features Page.