Label Studio From $99/mo · Free plan 8.9 Visit BRAT
brat.nlplab.org
What it is
brat is a free, open-source tool for structured text annotation, with annotations represented in forms computers can process. It supports text spans, binary relations, n-ary associations, attributes, normalization annotations, and freeform notes. Teams can configure categories, types, and constraints for their tasks, and multiple annotators can work on the same document or collection while seeing one another’s edits nearly as they happen. Normalization can link annotations to external resources, and brat can incorporate output from automatic annotation services available as web services. Its server and client support Unicode across nearly 100 scripts. The tool checks edits against configured constraints and searches documents or collections, including keyword-in-context concordancing. Annotations export in brat stand-off format; visualizations can be saved as SVG, PNG, PDF, or EPS. The free v1.3 release is self-hosted under the MIT License. New server installations assume a UNIX-like environment; Windows users can run brat in a UNIX-like virtual machine. The experimental standalone server is not security-hardened and is not recommended for sensitive data or systems accessible from the internet.
Spec sheet
- Purpose
- brat is a web-based tool for structured text annotation, where annotations have fixed forms that computers can process.Read 2 Oct 2026 · brat.nlplab.org
- Support
- The project directs usage questions to its mailing list and bug reports or feature requests to its GitHub issue tracker.Read 2 Oct 2026 · brat.nlplab.org
- Annotation types
- It supports text spans, binary relations, n-ary associations, attributes, normalization annotations, and freeform notes.Read 2 Oct 2026 · brat.nlplab.org
- Automatic annotation
- The tool can integrate output from automatic text annotation services accessible as web services.Read 2 Oct 2026 · brat.nlplab.org
- Collaboration
- Multiple annotators can work simultaneously on the same collection or document and see each other’s edits nearly as they are made.Read 2 Oct 2026 · brat.nlplab.org
- Configurable
- Annotation categories, types, and constraints are configurable for different text annotation tasks.Read 2 Oct 2026 · brat.nlplab.org
- Exports
- Annotations can be exported in brat stand-off format, and visualizations in SVG, PNG, PDF, or EPS.Read 2 Oct 2026 · brat.nlplab.org
- External resources
- Normalization can associate annotations with external resources such as Freebase, Wikipedia, and Open Biomedical Ontologies.Read 2 Oct 2026 · brat.nlplab.org
- 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.Read 2 Oct 2026 · brat.nlplab.org
- Languages
- The server and client support Unicode, including nearly 100 different scripts.Read 2 Oct 2026 · brat.nlplab.org
- Project origin
- The project says it was developed collaboratively by researchers from several groups interested in text annotation.Read 2 Oct 2026 · brat.nlplab.org
- 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.Read 2 Oct 2026 · brat.nlplab.org
- Validation and search
- brat validates annotations against configured constraints after edits and supports searches across documents or collections, including key-word-in-context concordancing.Read 2 Oct 2026 · brat.nlplab.org
Plans and prices
brat v1.3 (Crunchy Frog) Free Open source · MIT License · Self-hosted installation Read 2 Oct 2026 · brat.nlplab.org
Strong points and limits
Strong points
- Supports multiple structured annotation types.
- Annotators can see collaborators’ edits nearly in real time.
- Supports Unicode across nearly 100 scripts.
- Exports annotations and visualizations in several formats.
Limits
- New server installations assume a UNIX-like environment.
- The experimental standalone server is not security-hardened.
- Standalone server is not recommended for sensitive or internet-accessible systems.
Who it suits
brat suits teams doing configurable, collaborative text annotation who can manage a self-hosted installation. Its standalone server is not recommended for sensitive data or internet-accessible systems.
Verdict
brat offers configurable annotation, collaboration, validation, search, and export capabilities in a free, self-hosted release. Installation environment and standalone-server security limitations matter when planning deployment.
Where Specifiction places it
- AI Data Labeling Tools#9 of 228.0
