Like many gaming apps, Steam will start automatically when you sign in to your computer. This can lead to clogged bandwidth, as games update automatically or appearing online when you don’t mean to. Steam’s auto-start is easy to quickly turn off.
On Windows, click Steam > Settings to open the settings screen. On Mac, click Steam > Preferences to open the preferences screen.
Once you’re in the Settings or Preferences menu, click the “Interface” tab on the left side of the new window.
Next, look for the “Run Steam When My Computer Starts” checkbox and uncheck it.
When you’ve altered the setting as desired, click “OK” to close this menu and to confirm the setting.
If you’re playing on Windows 10, you can instead choose to disable startup programs via the Windows Task Manager. You can prevent certain programs from launching at boot on a Mac by opening System Preferences > Users & Groups > Login Items and unchecking the desired programs.