The Jet Set Willy code card is a copy protection device used to discourage software piracy.

In the 1980s, software piracy was becoming widespread in schools and playgrounds, and game companies were searching for ways to better protect their products.

Software Projects, determined to prevent their hit game Jet Set Willy from being easily copied, took extra precautions. At the time, anyone with a tape-to-tape recorder could duplicate games with ease.

To combat this, they included a brightly coloured card inside the cassette case, created in collaboration with Padlock Systems. This card featured a grid of letters and numbers, each corresponding to a specific sequence of four colours.

When the game loaded, players were prompted with a code, such as "A1". They had to refer to the card and input the matching colour sequence, such as Blue, Purple, Green, Blue, to start the game. Entering the wrong sequence would simply restart the prompt in an endless loop.

However, the system had its flaws. Many colour-blind players struggled to use the card effectively. Worse still, the instructions in early Spectrum versions were incorrect, leading players to enter the wrong codes. The card's small size, designed to fit within the cassette case, also made it difficult to read.