how to stop steam from opening on startup, follow these steps: Open the Steam client on your computer. Click on "Steam" in the top-left corner of the client. Select "Settings" from the drop-down menu. In the Settings window, navigate to the "Interface" tab. Uncheck the box that says "Run Steam when my computer starts." Click "OK" to save your changes.
Now, Steam won't launch automatically when you start your computer. If you ever change your mind, you can revisit the same settings and re-enable the option. This process may vary slightly based on your operating system, but the general steps should be similar.