I'm not sure if this has been shared before but I figured this out myself although there are probably guides already.
This works for games that dont need to connect to steam servers too play, its worked on every singleplayer offline game I've tried but you cant fail because you can still refund the game!
How to do it (I used the game crashlands for example)
Step 1: Buy the game
Step 2: Download the game
Step 3: Refund the game (Go to steam support on the steam client, select the game and press refund)
Step 4: Locate the games folder in the steam (I'm sure you know how to do this)
Step 5: Copy and paste the game folder out of the steam folder
Step 6: Open the folder and search for any steam_api files and delete them (sometimes there is none)
Step 7: Find the game .exe and run it
Step 8: Enjoy!
This is my first proper post so dont bully
You can fail the step 3 easily
ultrawtf (07-05-2016)
It does work. I did it with DCS. I bought the A10 and F15 then I sent a refund request, stating that the DLC causes major FPS drops and crashes the game at odd times. I was refunded, but still able to fly those planes freely whether I was online or offline. However, uninstalling and reinstalling the game will cause the DLC to permanently disappear due to not having a serial key associated to it.
Not free since it needs some investment
Nigga single player games?? Just torrent the bitch
x12 (07-05-2016)
It works but its a pain to have to use steam in offline mode. More convenient to just torrent a game if you really want it free imo
how about using kat.ph
Not your average fuckboy