Many modders intentionally "backport" or freeze their game at 1.6.640. This is because the transition from 1.6.640 to 1.6.1130 involved significant changes to the way the game handles plugins (the "Marketplace" update).
The Skyrim Script Extender (SKSE) is the absolute cornerstone of modding The Elder Scrolls V: Skyrim Special Edition . If you are looking for the , you are likely running the version of the game often referred to as "Pre-Update AE" (Anniversary Edition). skse 16640 link
While Bethesda has since updated the game to 1.6.1130 and 1.6.1170, the 1.6.640 build remains incredibly popular because of its stability and the massive library of compatible mods. Many modders intentionally "backport" or freeze their game
By staying on 1.6.640 with the corresponding SKSE link, you ensure: If you are looking for the , you
From now on, do not launch Skyrim through Steam. You must run skse64_loader.exe to start the game with mod support. Why version 1.6.640 is a "Golden Build"