What was the first console add-on to use CD-ROM technology for video games?

The PC Engine CD-ROM² was the first console add-on to use CD-ROM technology for video games.

NEC and Hudson Soft introduced the CD-ROM² System in Japan on December 4, 1988, as an add-on for the PC Engine. It allowed games to be distributed on compact discs rather than HuCard cartridges. CDs offered substantially more storage for music, spoken dialogue, animated scenes, and larger quantities of artwork than the console’s original media.

The system is sometimes confused with the TurboGrafx-16 CD or the TurboDuo. Those were later Western-market names and integrated products based on related PC Engine CD technology. Sega’s Mega-CD, known as Sega CD in North America, also arrived later, in 1991 in Japan.

CD-ROM² games were not automatically superior in every technical respect. They could have long loading times and sometimes used compressed or limited audiovisual assets. Nevertheless, the add-on marked an important transition from cartridge-based console software toward optical media.