Techniques and systems for auditing and augmenting user-generated tags for digital content are described. A corpus is generated for each tag associated with digital content to represent different aspects of the tag's definition. A hierarchy of semantic relationships between the tags is created based a corpus co-occurrence between the tags to relate at least two tags having different levels of specificity. Some of the tags are verified with the digital content based on feature detection, and a correspondence to the digital content is determined for each verified tag. The correspondence of the verified tags is then propagated up the hierarchy to others of the tags that are semantically related to the verified tags but which were not verified by the feature detection. The verified tags and the verified other tags are then assigned to the digital content to control how the digital content is retrieved when subject to a search.