What cable enabled Pokémon Red and Blue players to trade and battle?

The Game Link Cable enabled Pokémon Red and Blue players to trade and battle.

Each Game Boy cartridge could be played alone, but connecting two systems with the cable unlocked the series’ defining multiplayer features. Players could exchange Pokémon and compete in battles using teams they had trained.

Trading was essential because the paired versions contained different Pokémon. A player could not complete the original Pokédex using only one cartridge without trading with another game or receiving special distributions.

The cable also made Pokémon unusual among role-playing games of its era. A portable system designed mainly for single-player use became a social collecting device. Later hardware generations replaced the physical cable with wireless and internet-based communication, but the original Game Link Cable established the tradition.