LegacyAI is a software developed by Manticore Software that allows older Macintosh computers to communicate with AI services like OpenAI's ChatGPT. It can be used in 15 different Mac systems, ranging from System 7 to 10.11 (El Capitan). LegacyAI can be configured to fully customize the user's experience, using a proxy server to do so. Its main features include conversing with OpenAI's ChatGPT, image generation with DALL-E, the ability to save and load conversations for future reference, customization of AI models, and customizable preferences.

LegacyAI is free to use, but its API access is dependent on donations to cover running costs. Those who find LegacyAI useful and are in a position to donate are encouraged to do so. For additional features and AI models, a license can be purchased to support the project. Users can also sign up for a small monthly subscription to support the project.

It is important to note that LegacyAI does not transmit information over HTTPS. As Mac OS 7/8/9 was built before HTTPS became a standard protocol for transferring information over the internet, any transmissions made on an older Macintosh are insecure. Therefore, users are advised not to use LegacyAI for sensitive subjects.

LegacyAI is available for download in three versions: LegacyAI (68k) 2.4.0 (Macintosh System 7 - Mac OS 8.6), LegacyAI (PPC) 2.4.0 (Mac OS 8.1 - Mac OS 9), and LegacyAI (Universal Binary) 2.4.0 (Mac OS X - Mac OS X 10.11 El Capitan).

Manticore Software is a New Zealand-based agency founded and run by Jordan Trbuhovic. Users interested in tracking bugs or requesting new features can use the Bug/Feature Tracker on the website. The website was built using Sloop.