Steam likes to warn users about the dangers of being antisocial, so it will throw up a warning when you try to open Steam again, after closing it in offline mode. If you prefer Steam to open in the background, or like me, don't want your friends to know how much of a degenerate you are (wayyy too many hours of Skyrim), then this tutorial is for you.
Go to your Steam installation directory (typically C:\Program Files (x86)\Steam) and create a new text file that you'll rename to a .bat file. I called mine SteamOffline.bat. Open your new batch file with notepad and paste these lines:
Save your batch file and make sure it works by exiting Steam (shouldn't be running in Task Manager) and double-clicking the batch file to run it. Make everything neat by right-clicking your batch file and clicking Create shortcut. You can change the icon and rename the shortcut to look like the original Steam application.
You might notice that a terminal opens up briefly before Steam runs, then disappears. We can address this by making the program start minimized. Then, right-click your new shortcut and click Properties. In the drop-down menu labeled Run:, select Minimized, then click okay to close the properties window. You can now use this shortcut to replace all your Steam shortcuts to always start Steam offline.
Now we'll replace Steam's startup entry with a modified offline entry. In the upper left hand corner of the Steam menu, go to Steam > Settings > Interface and uncheck Run Steam when my computer starts.
Execute the Run command by pressing Windows Key + R and type shell:startup. The windows startup folder should open. Cut and paste your modded shortcut into the startup folder.
Open Command Prompt with Ctrl + Shift + Esc and navigate to the Startup tab. Verify that Steam is not there, and SteamOffline.bat, or whatever you named your batch file, appears on the list.
Reboot your computer and enjoy Offline Steam as it was intended!
btw, does anyone know how to make image thumbnails in Nexus Forums without resizing the actual image? This forum uses some really weird bbcode for images.
If it randomly stops working and the Offline Mode warning popup starts appearing again, open steam normally and see if it requests your username and password. If so, you need to sign in to steam again and remember to check the "Remember my password" box. Windows version updates, e.g. 1902 to 20H2 can cause apps to sign you out, resulting in some things breaking.
Edited by Levvine, 26 February 2021 - 02:18 AM.