Methods, systems, and apparatus, including computer program products are provided for indexing tags in source code. Implementations provide an enhanced retrieval of source code, in which a score for each of a plurality of files is derived based on a quantity of references to each file in source code of the remaining plurality of files. A query is received identifying a source code tag. Matching files of the plurality of files that satisfy the query are identified, a ranking of the matching files is generated based on the derived scores, and the ranking is provided.