Contents
In brief
extend.ai released Extend UI — an open-source set of 14 React components for document apps: PDF, DOCX, XLSX, CSV viewers, bounding box citations, uploads, and e-signature. MIT license, fully customizable; announced via Show HN.
What happened
A familiar product story: before shipping extend.ai, the team tried every file viewer and document UI kit they could find — missing formats or polish for user-facing flows. The internal component set grew into a product and is now open to the community.
The kit ships ready-made in-browser viewers, citation highlights tied to page coordinates (bounding boxes — useful for RAG review UIs), drag-and-drop upload, and signing. Targets customer apps, agent interfaces, and internal document workflows.
Authors publish a demo video and integration examples — not just an npm package in isolation. For teams building document AI or compliance tools, this removes months of viewer-layer work.
Why it matters
The LLM + documents space is crowded with parsing backends, but the frontend for “human sees file, model cites a paragraph” is often bespoke. Off-the-shelf viewers are proprietary, expensive, or dated. Extend UI fills that gap — React, MIT, modern office formats beyond PDF-only.
Document-centric products are standardizing the display layer like tables and date pickers once did. Components are not tightly locked to extend.ai’s backend.
In practice
- Need one viewer for PDF + Office? Extend UI covers both.
- For RAG review, inspect bounding box citations — users see source regions.
- Confirm MIT and fork freedom for corporate theming.
- Compare with react-pdf / paid SDKs on DOCX/XLSX and e-sign.
- Start from demo and examples on the site.
- Budget theming time — customizable, but design tokens are still yours.
Takeaway
Extend UI is a product team open-sourcing the UI layer they built for themselves. Building around contracts, filings, or AI file review? Spend an hour on their kit before stitching three libraries. Docs and demo: extend.ai/ui.