The valve is test options The new Steam client beta will force you to download updates only when you launch the game by default.
Currently, by default, Steam determines which game updates to download based on a few different things. Valve explains:
For games you’ve played recently, Steam will download updates for the game as soon as they’re released. For games you haven’t played in a while, Steam may choose to wait a few days to bundle multiple updates together or download updates while you sleep.
A new default option to wait for updates to download gives players more control. As Valve points out, this means users can hold off on major game updates until they actually want to play them, which could be a relief for those with bandwidth limitations.
The new option is available in the beta Steam client settings.[ダウンロード]It’s in the section. “You can set the defaults to either let Steam decide when to update your game (based on factors like when you last played the game, bandwidth availability, etc.) or when the game is launched. or wait for the update until later,” Valve said.
It’s still possible to set per-game download settings that override global settings in the game’s properties, but Valve says the “descriptions” of these options have been “cleaned up.” The beta also allows you to manage per-game overrides in Download Settings across the Steam client.