The Konami Code and Other Famous Cheat Codes, Explained

By s-coding23 · October 30, 2026 · 6 min read

Before the internet, cheat codes spread through magazines, playground rumours and the backs of game boxes. A few became so famous that people who never played the games still know them. Here are the legends, where they came from, and how to use them.

The Konami Code

Up, Up, Down, Down, Left, Right, Left, Right, B, A. It first appeared in Konami's home version of Gradius, where a programmer reportedly added it to make the game easier to test, and it powers up your ship. It became world-famous through Contra on the NES, where entering it on the title screen (followed by Start) gives you 30 lives instead of 3. Konami went on to hide it in dozens of other games, and it still turns up as an Easter egg on websites and apps today.

Mortal Kombat's blood code

When Mortal Kombat came to home consoles in 1993, both versions toned down the arcade's gore. The Super Nintendo version replaced the blood with grey "sweat". The Genesis version hid it instead: on the screen that explains the "Code of Honor", press A, B, A, C, A, B, B and the blood and finishing moves come back. That hidden code helped the Genesis version outsell its rival, and the debate over violent games that followed led to the creation of the ESRB age ratings.

Sonic the Hedgehog's level select

In the original Sonic the Hedgehog, press Up, Down, Left, Right on the title screen. If you hear a ring chime, hold A and press Start to open a level select. Sonic 2 has its own: in the sound test, play tracks 19, 65, 09 and 17 (said to be the birthday of programmer Yuji Naka), then return to the title screen, hold A and press Start. Codes like these were left in by developers for testing and kept because fans loved finding them.

JUSTIN BAILEY

Metroid used passwords instead of saves, and players discovered that the password JUSTIN BAILEY (with dashes filling out the rest of the password grid) starts the game with lots of equipment and Samus out of her armour. For years people assumed Justin Bailey was a real person; the truth is that the password system simply turns some combinations of letters into valid game states, and this one happened to spell a name.

ZELDA

In the original The Legend of Zelda, finishing the game unlocks a harder Second Quest with rearranged dungeons. You can skip straight to it by entering ZELDA as your name on the file screen.

Codes vs cheat devices

All of the above were built into the games by their developers. Cheat devices like the Game Genie, Action Replay and GameShark were different: they changed the game's memory as it ran, which let players invent codes the developers never planned, such as infinite lives in games that had no cheats at all. Our guide to using retro cheat codes explains how those devices worked and how to enter their codes in an emulator, and every game on Matrix Picks with known codes has its own cheats page. Start with the cheat code search.

Do these still work?

Yes. Built-in codes work on original cartridges, in emulators, and in most official re-releases, because they're part of the game itself. If a code doesn't seem to work, check that you're playing the right version: codes sometimes differ between the Japanese, American and European releases of a game.