client. Version 1.28.5 was originally released on July 6, 2017, and is highly valued by the community for its stability and improved mechanics before the Reforged update. Blizzard Forums How to Download and Install Version 1.28.5
click the "Battle.net" button inside the game menu. Doing so will immediately trigger a ~30GB download that overwrites your classic files with the Reforged client. Pre-installed Files: Community hubs like The Hive Workshop
Use the -windowpane shortcut target to run the game in a borderless window, which helps with alt-tabbing.