This release is available without DRM.

A separate runtime usually shipped with digital releases of games from marketplaces like DMM or DLsite. Requires a Soft-Denchi account to activate the same product on multiple systems. Official website.

Used by DLsite. It can have a limit of 3 or 5 activations per game, depending on the title. An internet connection is required for installation and authentication.

Used by many Steam titles. Requires the Steam Launcher to play.
If the title can't detect that the launcher is running, it won't start, opening Steam instead. In some cases, it can boot the player out of the game or, in extreme cases, stop responding at all.

Requires an internet connection each time the game is installed.

These games ask for a serial or product key during installation.

Unknown disc check DRM implementation.

Games that requires a constant internet connection. Any loss of connection will boot the player out of the game.
Common in many online games, like gacha games or social games.

Requires a Buddy account and the Buddy Launcher for activation, which are later used each time a game is launched. Needs an internet connection at launch. Official website.

SafeDisc is a copy protection program for Microsoft Windows applications and games distributed on optical disc. Created by Macrovision Corporation, it was aimed to hinder unauthorized disc duplication. The program was first introduced in 1998 and was discontinued on March 31, 2009.

Not supported since Windows 10, nor previous versions of Windows with the KB3086255 update installed due to security concerns. Restoral is possible using a non-intrusive SafeDiscShim compatibility tool.

Disk encryption scheme by SETTEC, common in many 2000-era physical games.
If the Disc Check failed to work properly, the serial number that came with the game can be input into the SETTEC website to get a file which is placed in the directory of the EXE.

Provided by Interlex, Inc, this DRM was retired in 2010, and all games that previously used the system are now DRM free. Before that, it was limited to three activations and required an online authentication every time at launch.

Users who own the older physical versions of these games can download a patch to remove the DRM:
* Uninstall V-Mate from your machine.
* Download your game's patch at link
* Manually replace your game's file with the patched file.

Limited to five daily activations per game, which resets 24 hours after the first activation. Stores licensing data (the "offline token" used to launch the game) separately on the storage drive. However, it requires an online connection periodically to renew this token.
More information on PCGamingWiki.

Ring Protect was renamed to StarForce at 4th version. Compared to the modern variant, doesn't check CD-key.

Used by DLsite for Android games. Requires DLsite's own Android application for installation.

5 time activation limit.

Protects the executable file by running a protection code in a virtual CPU, usually to avoid cracking and modding. This might require higher system requirements than usual for the end user.
It can also store and process purchase orders, generate registration keys and store customer information in a database.
Created by a company with an unknown HQ location with physical addresses in at least 3 different countries, but it's highly probable it's from Russia.

[From the official website and Steam forums]

Physical DRM checks, such as manual checks or codewheels.