Compared to its predecessor, Doom II features larger levels, new enemies, a new Super Shotgun weapon, and a new power-up.

The release of the Doom source code has facilitated ports to platforms including iOS and other cellphone systems.

However, because the levels are nonlinear players can wander off the beaten path, and those that do are often rewarded with bonuses, like health pickups and more powerful weapons.

Nowadays, in the modern standards, Doom II can be played with almost any version of Windows across the internet using third-party source ports such as Odamex,[5] Zandronum,[6] ZDaemon,[7] and are still popular today.

[9][10] The humans who survived the attack have developed a plan to build massive spaceships which will carry the remaining survivors into space.

[11] Just as he sits down to await death, knowing that he saved humanity, the marine then receives an off-planet transmission from the survivors in orbit, who have managed to find out where the armies of Hell are coming from.

After fighting through the hordes of Hell, the marine reaches the location of the biggest demon he has ever seen, called the Icon of Sin (Baphomet).

The marine wonders where evil people will go when they die now that Hell has been destroyed, and reflects that rebuilding the world will be more fun than saving it as he begins his journey back home.

[17] Doom II was released for DOS on October 10, 1994 (one of the days of the Doomsday rule and exactly ten months after the original) in North America and Europe.

[29][30][31] The release of the Doom source code has facilitated ports to many other platforms, including iOS and other cellphone systems.

Back in 1995, some retailers were selling disks in stores that simply contained many Doom WADs scraped from the internet.

Though the levels were available for free online, many players had slow internet access at the time and so would purchase the disks, which were "selling like hot-cakes".

Realising this, id decided to officially license a similar disk- by approaching mappers and commissioning them for levels, in addition to the large shareware collection.

More broadly, the disk was part of an effort by Romero to diversify id Software's income at a time when much of the team was waiting for the Quake engine to be ready.

Although no detailed plot information is given, this expansion appears to take place after the main campaign of Doom II.

Brandon James, president of Nerve Software, said this expansion was designed to be played on Ultra-Violence difficulty, contains "a plethora of secrets to find," and "is geared toward a more hardcore experience.

The new episode is divided into two chapters, "The Vulcan Abyss" and "Counterfeit Eden," which contain a combined total of 16 maps.

[51] The game was reviewed in 1995 in Dragon #216 by David "Zeb" Cook in the "Eye of the Monitor" column, who stated that, "if mindless but intense carnage is what you want, you'll get your money's worth.

This led PC Data to declare it the country's third-best-selling computer game for the period between January 1993 and April 1998.

[61] In 2022, John Romero created a new level called "One Humanity"[62] for the game to raise money for the Ukrainian Red Cross, and the United Nations Central Emergency Response Fund following the outbreak of the 2022 Russian invasion of Ukraine.