Extracting and tagging metadata for evidence synthesis takes an average of 25.3 days for systematic maps (Haddaway and Westgate 2018). Since many types of metadata, such as location of study or focal species, also function as eligibility criteria to include studies in a synthesis, the total amount of time spent considering metadata for a systematic map could be upwards of 100 hours. topictagger partially automates the process of tagging metadata and document topics for evidence synthesis. Given a hierarchical ontology of relationships between entitites, a set of articles with known topics, or a set of terms associated with a topic, topictagger will tag metadata from an ontology or classify articles by probable topics (e.g. outcomes) and return probable topics and metadata tags for each article.