Extend UI
Open-source React UI kit for document apps — PDF, DOCX, XLSX, and CSV viewers with citations and e-signing built in.
Pricing
- All components free
- MIT license
- Self-hosted
- GitHub source access
Key Features
- PDF, DOCX, XLSX, and CSV viewer React components
- Bounding box citation overlays for AI-grounded document UIs
- File upload and file system browser components
- E-signing component for document workflows
- Schema builder and document splits view
- Drop-in ready for agent pipelines and internal tools
Pros & Cons
Pros
- Fully open source with ~1.4k GitHub stars at launch
- Covers all major document formats in one kit
- Citation/bounding-box support is rare and directly useful for RAG and AI document apps
- Ready for agent or user-facing flows without custom wiring
Cons
- React-only — no Vue, Angular, or web-component variants
- Maintained by Extend AI, so roadmap may favor their own product needs
- Niche scope limits reuse outside document-centric apps
- No hosted or managed option — purely a self-integrated library
Extend UI fills a real gap: document viewer components that understand AI citations and agent contexts, not just passive file rendering. For teams building RAG interfaces, document automation, or internal tools around PDFs and spreadsheets, it's a meaningful head start. The React-only constraint and Extend AI stewardship are the main reasons to evaluate longevity before committing.
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