Like many game apps, Steam starts automatically when you log in to your computer. This can lead to clogged bandwidth, as games update automatically or appear online when you don't plan to. Steam auto-launch is easy to disable quickly.
In Windows, click Steam> Settings to open the settings screen. On Mac, click Steam> Preferences to open the preferences screen.
Once you are in the Settings or Preferences menu, click the "Interface" tab on the left side of the new window.
Next, check and uncheck the box "Run Steam when my computer boots".
When you have set the setting as desired, click "OK" to close this menu and confirm the setting.
If you're playing on Windows 10, you can instead choose to disable startup programs through Windows Task Manager. You can prevent certain programs from starting at startup on a Mac by opening System Preferences> Users & Groups> Login Items and turning off the desired programs.
RELATED: Managing Startup Applications in Windows 8 or 10