Enlarge (credit: Getty Images) On Tuesday, OpenAI announced fine-tuning for GPT-3.5 Turbo—the AI model that powers the free version of ChatGPT—through its API. It allows training the model with custom data, such as company documents or project documentation. OpenAI claims that a fine-tuned model can perform as well as GPT-4 with lower cost in certain scenarios. In AI, fine-tuning refers to the process of taking a pretrained neural network (like GPT-3.5 Turbo) and further training it on a different dataset (like your custom data), which is typically smaller and possibly related to a specific task.