"Brat is a web-based tool for text annotation". Brat is particularly designed for structured annotation where the textual notes are fixed and can be easily categorized in order to aid automated computer processing and interpretation. Brat facilitates four types of fixed annotations: text span annotations, suitable for creating categorical annotations for entities; relation annotations, suitable for drawing simple relationships between entities; n-ary associations, that link annotation to specific roles; and finally normalization annotations, that associate internal annotations with external resources. All annotations can be further explained and categorized using attributes that describe the base annotation - similar to how adjectives modify a noun. Brat's user-friendly and intuitive features include comprehensive visualization, editing, integration with resources, annotating in any language, and easy export in multiple formats.