Playing around with Steam offline mode is somewhat tricky, since it sometimes just won't work. Anyway, you can create a local copy of the
steam.cfg file with the following settings in it:
BootStrapperForceSelfUpdate = disable
Put the newly created
steam.cfg file in your Steam directory and it should start in offline mode.
Doing it automatically based on your internet connection may be possible, if you know how to achieve this using a Batch file. This would be something for Stackoverflow, though.
The steps you'd need to do:
- Create the mentioned config file as
somethingelse.txt inside your Steam directory.
- Check for connectivity (maybe use this answer from SO).
- If offline, put the
steam.cfg mentioned above in place:
- Have your steam.cfg file ready, but under a different name, that's why I called it
(If it's there, Steam is offline. Period.)
RENAME somethingelse.txt steam.cfg
- If online, do (almost) nothing.
- Remove/rename existing
steam.cfg file, if it's still present from a previous session.
- Start Steam.
You could achieve this by using a single Batch file (the one in 1.), but it's not as easy as it looks.
Starting Steam directly in online mode without the Batch file would still require you to look for the presence of the
steam.cfg file, unless you're sure it's not there or at least renamed. No
steam.cfg, no harm.
This answer covers only how to actually get into offline mode forcefully. If you didn't install, update & save your games properly you can not play them in offline mode. If you didn't save your login credentials (and exit Steam gracefully) you can not use the offline mode at all. Make sure to test everything while still being connected to the internet.
Also if your settings get saved even with having the file removed, just revert them (
ForceOfflineMode=disable) and keep them as new
steam.cfg file for the next launch.