Service that lets you train custom image classification and object detection models by uploading your own labeled images, without needing machine learning expertise. Microsoft announced its retirement, with support until September 25, 2028.
In AI-901 it's distinguished from Azure AI Vision (generic pretrained models): Custom Vision is used when you need to recognize business-specific objects or categories (e.g., distinguishing specific product models) that the generic model doesn't recognize. As alternatives, Microsoft recommends Content Understanding, a multimodal model in Foundry, or Azure Machine Learning AutoML.
Azure AI Custom Vision is a concept that can show up on the exam. Check the full guide to see it in context.