What Azure Cognitive Services feature is best for automatically tagging images on social media?

The feature that is best for automatically tagging images on social media is Computer Vision. This service is designed to analyze images and understand their content. By using machine learning models, Computer Vision can recognize objects, scenes, and activities within an image. This capability allows for the automatic tagging of images, generating relevant keywords that describe their content, which is particularly useful for sorting, searching, and improving user engagement with social media posts.

Conversely, Speech Recognition primarily deals with converting spoken language into text, making it less relevant for image tagging. Text Analytics focuses on extracting insights from textual data, such as sentiment, key phrases, and named entities, which doesn't apply to image data. Language Understanding is aimed at comprehending the intent behind spoken or written language, which is also not applicable for tasks related to image analysis. Thus, Computer Vision stands out as the most appropriate service for automating the tagging of images based on their visual content.