BRAT
What it is
brat is a free, open-source web-based tool for creating structured text annotations in fixed forms that computers can process. It supports text spans, binary relations, n-ary associations, attributes, normalization annotations, and freeform notes. Annotation categories, types, and constraints can be adjusted for different tasks. Multiple annotators can work on the same document or collection and see one another’s edits nearly as they happen. Normalization can connect annotations with resources such as Freebase, Wikipedia, and Open Biomedical Ontologies, while the tool can incorporate output from automatic annotation services available as web services. Its server and client support Unicode, including nearly 100 scripts. brat checks annotations against configured constraints and can search collections or documents, including keyword-in-context concordancing. Annotations export in brat stand-off format; visualizations can be saved as SVG, PNG, PDF, or EPS. The v1.3 release is self-hosted under the MIT License. New server installations assume a UNIX-like environment, and the experimental standalone server is not security-hardened or recommended for sensitive data or systems accessible from the internet.
For and against
For
- Free and open source under the MIT License.
- Supports multiple annotators editing shared documents.
- Configurable annotation categories, types, and constraints.
- Unicode support includes nearly 100 scripts.
- Exports annotation data and several visualization formats.
Against
- New server installations assume a UNIX-like environment.
- Standalone server is not security-hardened.
- Standalone server is not recommended for sensitive data.
The verdict
brat offers detailed annotation types, configurable constraints, and shared editing in a self-hosted tool. Its experimental standalone server has explicit security limits, so the guide recommends a full web server for production.
Who it suits
brat suits teams doing structured text annotation that need configurable labels, concurrent work, and exportable visualizations. It is a fit for users able to manage a self-hosted installation in a UNIX-like environment.
Plans and prices
brat v1.3 (Crunchy Frog)
Open source · MIT License · Self-hosted installation
Read 2 Oct 2026 · brat.nlplab.org
On the record
- Annotation types
- It supports text spans, binary relations, n-ary associations, attributes, normalization annotations, and freeform notes.brat.nlplab.org · read 2 Oct 2026
- Automatic annotation
- The tool can integrate output from automatic text annotation services accessible as web services.brat.nlplab.org · read 2 Oct 2026
- Collaboration
- Multiple annotators can work simultaneously on the same collection or document and see each other’s edits nearly as they are made.brat.nlplab.org · read 2 Oct 2026
- Configurable
- Annotation categories, types, and constraints are configurable for different text annotation tasks.brat.nlplab.org · read 2 Oct 2026
- Exports
- Annotations can be exported in brat stand-off format, and visualizations in SVG, PNG, PDF, or EPS.brat.nlplab.org · read 2 Oct 2026
- External resources
- Normalization can associate annotations with external resources such as Freebase, Wikipedia, and Open Biomedical Ontologies.brat.nlplab.org · read 2 Oct 2026
- Hosting requirements
- A new server installation assumes a UNIX-like environment; the installation guide says Windows users can run it in a virtual machine with a UNIX-like operating system.brat.nlplab.org · read 2 Oct 2026
- Languages
- The server and client support Unicode, including nearly 100 different scripts.brat.nlplab.org · read 2 Oct 2026
- Project origin
- The project says it was developed collaboratively by researchers from several groups interested in text annotation.brat.nlplab.org · read 2 Oct 2026
- Purpose
- brat is a web-based tool for structured text annotation, where annotations have fixed forms that computers can process.brat.nlplab.org · read 2 Oct 2026
- Security limitation
- The experimental standalone server is not security-hardened and is not recommended for sensitive data or systems accessible from the internet; the guide recommends a full web server for production.brat.nlplab.org · read 2 Oct 2026
- Support
- The project directs usage questions to its mailing list and bug reports or feature requests to its GitHub issue tracker.brat.nlplab.org · read 2 Oct 2026
- Validation and search
- brat validates annotations against configured constraints after edits and supports searches across documents or collections, including key-word-in-context concordancing.brat.nlplab.org · read 2 Oct 2026
