The Blood Code That Changed Mortal Kombat on Genesis

On September 13, 1993, Mortal Kombat reached home consoles in a heavily promoted launch called “Mortal Monday.” Players who bought the Sega Genesis version soon learned that the most important feature was not printed in the manual. At the opening “Code of Honor” screen, they could press A, B, A, C, A, B, B. That seven-button sequence—ABACABB—turned on red blood and the more graphic finishing moves included in the port.

The code was simple enough to memorize and strange enough to feel like forbidden knowledge. It spread through game magazines, friends, and schoolyard conversations. More importantly, it changed how people compared the Genesis and Super Nintendo versions. A hidden option became part of a much larger argument about censorship, console identity, and who should decide what players were allowed to see.

Bringing the arcade controversy home

Midway released the original Mortal Kombat in arcades in 1992. Its digitized actors gave the fighters a more lifelike appearance than many cartoon-style games of the period. Blood sprayed during hard hits, and a winning player could perform a “Fatality” that ended the match with a violent scene. The fighting system mattered, but the shocking presentation was a major reason crowds gathered around the cabinet.

Publisher Acclaim wanted versions for the leading home systems while interest was still high. The company assigned the Genesis port to Probe Software in the United Kingdom and the Super Nintendo port to Sculptured Software in Utah. Both teams had to shrink an arcade game made for powerful, specialized hardware onto cartridges for less capable machines. They also faced very different rules from Sega and Nintendo about violent content.

Two ports with two different answers

Nintendo required the Super Nintendo team to remove the arcade game’s red blood and change several Fatalities. Hits produced gray drops that were described as sweat, while some finishing moves were made less graphic. The finished cartridge did not include an official built-in code that restored the missing blood. Its graphics and sound had strengths, but many players felt that it did not deliver the full experience they remembered from the arcade.

The Genesis game also began in a cleaned-up state. Its difference was that the violent effects remained available behind a secret input. Entering ABACABB switched on the red blood and more graphic presentation that Probe had placed in its version. The code did not make the port identical to the arcade machine; compromises in animation, sound, color, and controls still existed. Yet to shoppers comparing two cartridges with the same name, the Genesis edition now had a powerful advantage: it offered a choice the Super Nintendo release did not.

How ABACABB was built

Probe programmer Paul Carruthers later explained that ABACABB was not the first password used during development. His original seven-letter code was DULLARD: Down, Up, Left, Left, A, Right, Down. It opened a larger diagnostic menu that let testers change several options, including blood. Near the end of production, the publishers wanted a simpler sequence made only from the Genesis controller’s A, B, and C buttons.

According to Carruthers, someone at Sega suggested ABACAB. His existing code checker expected seven inputs, however, so the two sides settled on ABACABB. Fans often connect the letters to Abacab, the 1981 album by the band Genesis. That resemblance is wonderfully appropriate, but Carruthers’ account only confirms the suggestion from Sega and the need for a seventh character. The popular album explanation should be treated as a clever possibility, not a proven origin story.

The finished code was almost ideal for word-of-mouth. It did not require a difficult move, an accessory, or hours of play. Anyone could enter it before the first match. The sequence was also easy to copy into a notebook or recite to a friend. Like the Konami Code, ABACABB showed that a developer tool or secret setting could escape its technical purpose and become part of gaming culture.

Seven buttons in the console war

During the early 1990s, Sega marketed the Genesis as a faster and more rebellious alternative to Nintendo’s family-friendly image. The blood code fit that message perfectly, even though it was hidden. Players did not need an advertisement to explain the difference. They could watch the two versions side by side, enter seven buttons on one of them, and immediately understand which company seemed more willing to show the arcade violence.

That comparison could overwhelm every other detail. The Super Nintendo port had technical qualities that some reviewers preferred, while the Genesis conversion had its own limitations. Still, the question many buyers asked was much simpler: “Which version has the blood?” The answer made the Genesis cartridge the less-censored choice in the public mind. A small piece of programming had become a feature, a sales argument, and an unofficial symbol of Sega’s attitude.

The way the secret spread also mattered. Carruthers recalled that magazines and word of mouth quickly carried it to players. Keeping the feature out of the manual did not keep it obscure for long. Instead, discovery made it more exciting. Players felt as if they were unlocking something the adults, stores, or console companies had tried to hide, even though the developers and publishers had deliberately shipped the code inside every cartridge.

From Mortal Monday to a national ratings system

The home release placed arcade violence directly into millions of living rooms, where parents and lawmakers could see it without visiting an arcade. Mortal Kombat was not the only controversial game of the period, and ABACABB did not cause the political response by itself. However, the sharp contrast between the Genesis and Super Nintendo versions made the lack of a shared content standard easy to notice.

On December 9, 1993, a U.S. Senate hearing led by Senators Joseph Lieberman and Herb Kohl examined violent video games and the need for ratings that would help parents understand what they were buying. A second hearing followed in March 1994. Industry representatives promised to build a credible system rather than wait for a government commission. The result was the Entertainment Software Rating Board, founded in 1994 with five original rating categories and 17 content descriptors.

Ratings did not ban blood or end arguments about violent games. They created a common way to describe content on the package before a purchase. In that sense, ABACABB belongs to a short period when console makers could offer dramatically different versions of the same game and leave players to discover the difference through rumors. The controversy helped push the industry toward clearer labels, even as secret codes remained part of the fun.

Why the code still matters

Most cheat codes make a game easier, give the player extra lives, or unlock a hidden character. The Mortal Kombat blood code did something more unusual: it changed the game’s public identity. Without it, the Genesis port would have been another edited home conversion. With it, the cartridge became evidence in the console war and a lesson in how quickly players could share information before social media.

ABACABB also shows why context matters when remembering game history. The code was not simply a prank slipped past Sega, and it did not magically reproduce every arcade detail. It was a planned compromise inside a commercial product. Sega could ship a tamer default presentation, while informed players could switch on the version they wanted. The fact that nearly everyone became “informed” was what made the compromise so memorable.

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