Go grab yourselves some lunch, kids... This is going to be a long one.

I think everyone here will agree that DRM-free games are better than being restricted by online-dependent measures, but it's also hard to deny the fact that if you want to play most triple-A games on the PC, you're going to have to go through Steam. For a lot of games, that's actually okay; the GOG community thread here (https://www.gog.com/forum/general/steam_games_you_can_play_without_the_steam_client/page1) and the GOG community-maintained wiki page here (http://steam.wikia.com/wiki/List_of_DRM-free_games) has a list of Steam games that are actually DRM-free, games that only absolutely require Steam as a delivery service and nothing more. But most Steam games do, at the very least, require the client to be running and the user to be logged into an account. In fact, if a game isn't listed on the wiki, then it most likely falls into this Steam-required category, meaning that if Steam goes down, you won't be able to access your games.

Right? Not exactly.

Using Steam's Offline Mode, it's actually possible to play your Steam games offline forever, no matter what PC you're using, and transfer them from machine to machine without ever needing to go online to activate, verify, validate, or ask permission to play the games you've purchased. There are some exceptions, which I'll explain after going through the main walkthrough of how to do this, but the vast majority of Steam games will actually allow it to happen.

Keep in mind that NOTHING I'm doing here is illegal or against Valve's rules; I am using Steam 100% the way it's meant to be used, with no outside software or hacks/cracks of any kind. The method I'm showing you to keep Steam offline forever is built into the client itself. I'll be outlining how to do this in Windows, but the process should be exactly the same on Mac and Linux (I've been doing this in both Windows and Linux without any issues). Also, I've personally tested this method with PCs that were freshly built and completely offline, not even connected to a local network, just to make sure that everything worked flawlessly.

SETTING EVERYTHING UP:

It may surprise you to find out that, as far as I can tell, Steam is never actually “installed” to a PC, per say; Steam is simply downloaded and extracted to a folder on the hard drive. If you go through your Windows registry, the only Steam entries in there involve shortcut information. Steam is 100%, completely and totally portable, and can simply be copied and pasted to any PC at any given time.

First, start Steam and start up any games you want to be able to play in the future. Some games actually do require this so they can generate any necessary-to-run files, so it's always better to be sure. I usually run a game once immediately after it's done downloading, just to get it out of the way.

After you run all the games you want to keep, MANUALLY put the Steam client into Offline Mode. This is key, because if you don't do this, some files may still be dependent on Valve's servers. After putting it into Offline Mode, close the client; you now have a few different options.

Personally, I moved every one of my Steam games out of the SteamApps folder and zipped up the entire Steam folder separately. I did this specifically so I could have absolute control over which games I back up and which ones I don't, and so I could also update the Steam client and library files without having to mess with any games in the process. If you don't want to get that specific, you can literally just copy the entire Steam folder to an external drive or disc, and you'll be good to go.

After copying the Steam folder and any games to an external device, plug that device into a new PC; offline, if you want to test everything out. Simply start the Steam client from the Steam folder itself, select the option to stay in Offline Mode (or type in your password to "log in," even though being completely offline will still work perfectly fine), and you're pretty much done. You'll see your account username at the top of the Steam window even though you're offline, and the games you backed up will run. If the games are no longer in the SteamApps folder, however, you'll either have to start the games from their respective folders or change your Steam library location in the Steam options.

WHICH GAMES WON'T WORK?

There are three types of games that don't work using this method: games with third-party DRM (like Games for Windows: LIVE, Uplay, etc.), games that have Valve's CEG DRM built into them, and games that utilize Denuvo Anti-Tamper.

CEG stands for Custom Executable Generation, and it's exactly how it sounds: A game with CEG creates a special .exe file that's locked to the machine that initially downloads the game. If you move that game installation to a new PC, it won't run until a brand-new .exe file is downloaded. That's right: machine-specific games.

Denuvo Anti-Tamper is another method of locking games to a single machine by using .dlf files or dbdata files, the latter of which is located in a Steam game's userdata folder. Denuvo claims that Anti-Tamper is only supposed to prevent games from being modified, but I followed my own guide to try to play Metal Gear Solid V: The Phantom Pain on a friend's machine, and my unmodified, legally downloaded files didn't work. Denuvo is usually listed on any Steam store pages that use it, but there are exceptions, so always check online to see what people have found if you want to know if it's there. This Steam curator is a really good place to start: https://store.steampowered.com/curator/26095454-Denuvo-Games/

Checking for CEG is simple: Go to https://steamdb.info/, find your game, and click the Configuration tab. If you see anything that says checkguid or cegpublickey, then the game has CEG, and you can't move it around using this method. It's unfortunate, but I still haven't found any way of moving CEG-laden games without being online and redownloading machine-specific files.

Keep in mind that I believe this website only refers to the Windows versions of games, as the Linux versions of games listed as having CEG actually do not (I've tested many Linux versions of these games myself); either that, or CEG works completely differently in Linux. I believe the same can be said of the Mac versions of Steam games, but I don't have a Mac on which to do any testing.

OTHER NOTES:

In order for this to work, you do have to be playing the games using an offline account that has legally purchased the games in question. This means that you can't just copy your games to a friend's offline account and expect them to work, and personally, I'm absolutely fine with this. Every time you start your Offline Mode Steam client, you'll see your chosen username at the top, and that's how you'll know you're in the right profile.

This next tip isn't a requirement, but it sure helps: Delete everything in the Steam\appcache\httpcache and Steam\tenfoot\config\httpcache folders before moving or zipping the Steam folder. Those folders hold all of the cached files for Steam in both its regular mode and in Big Picture mode. The files aren't big, but there are a TON of them, and they make copying the Steam folder to an external device take much longer than it needs to take.

You can also, as far as I can tell, delete the Steam\depotcache folder. There can be a lot of files in there, some of them pretty big, that don't seem to be used for anything other than storing encrypted pre-loaded games. If a game you want to keep has already been released and is already fully downloaded to your hard drive, I don't believe the depotcache folder is necessary any longer.

Finally, something I figured out the hard way: If you move your Steam folder from an older version of Windows to a newer version, you may need to go online upon starting the client for the first time on that machine. I moved my Steam folder from my Windows 7 laptop to my Windows 8 desktop, and it needed to download some required files to be able to run Steam in Windows 8 that were not needed for it to run in Windows 7. After that initial download, however, everything worked flawlessly; I then transferred the same setup from my Windows 8 desktop to a friend's Windows 8 desktop, and it merely needed to run as an administrator the first time to set up the shortcuts in the registry.

UPDATE: If you move from Windows 8/8.1 to Windows 10, no additional files will need to be downloaded.

I hope at least a few people here find this guide useful. I'm fairly new to the world of PC gaming (I grew up playing nothing but consoles, from way back when the NES was new), and I've absolutely fallen in love with it, but I can't stand the restrictions that are built into so many digital game nowadays. I'm a retro gamer, I'll be playing these games for years and years to come, and I don't want to lose access to any of them. I actually really like Steam as a client, but I can't stand it as a DRM; being able to play my games offline forever, though, has given me a reason to actually pay attention to Steam games, and I couldn't be happier about that. It's not a DRM-free solution, and I'll always buy from GOG before anywhere else if possible, but this is definitely something I can work with. I don't know if this guide will get really popular or not, but if it does, I hope I haven't contributed to any changes to Steam in the future that will prevent us from doing all this.