brat rapid annotation tool (brat)

brat rapid annotation tool, is a free, open-source, web-based tool for text annotation visualisation and editing.

brat is fully configurable and can support a wide variety of annotation tasks, including, for example:

* entity mention ("named entity") annotation
* binary relation annotation
* dependency syntactic annotation
* structured, n-ary event annotation
* attribute/meta-knowledge annotation (e.g. negation, speculation, etc.)

The tool also provides annotation support features such as text and annotation search with detailed constraints, keyword-in-context concordancing, and integrated configurable checking of task-specific semantic constraints.

brat is developed as a collaborative effort between several research groups as an open source project (MIT license), and we warmly welcome contributions and participation from the community, including feature requests.


Pontus Stenetorp
Sampo Pyysalo
Goran Topić
Tomoko Ohta
Sophia Ananiadou
Jun’ichi Tsujii

Associated Institutions

University of Tokyo
National Centre for Text Mining
National Institute of Informatics

Resource URL
Application Domains
  • Domain independent
Other Resource Type
Software Subtype
Programming Languages
  • Other
  • Python
Operating Systems
  • Linux
  • OS X
  • Unix
  • Windows
Included Components
  • Application Programming Interface
  • Graphical User Interface
  • Library of modular components
  • Plug-in to other software
Dataset Subtype
Data Model Subtype
Online Resource Subtype
Knowledge Base Subtype
Intended User Types
  • Clinician
  • Clinical researcher
  • Informatics researcher
  • NLP researcher or developer
  • Software developer

Pontus Stenetorp, Sampo Pyysalo, Goran Topić, Tomoko Ohta, Sophia Ananiadou and Jun’ichi Tsujii. brat: a Web-based Tool for NLP-Assisted Text Annotation. In Proceedings of the Demonstrations Sessions at EACL 2012, Avignon, France, April 2012. European Chapter of the Association for Computational Linguistics.

Available Documentation
  • API
  • Included demo/tutorial data
  • Screenshots
  • Text/pictures
  • Tutorial
  • Web page/HTML documentation
Licensing Type
MIT License
Date of Latest Version