Extend UI

shadcn registry of PDF, DOCX, XLSX and CSV viewers with bounding-box citations

Tier A · StrongRegistryComponent LibraryBlock Collectionui.extend.ai

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Extend UI is the internal component layer Extend uses for document-heavy products, released as a 55-item shadcn registry under the @extend namespace. Beyond a standard shadcn base (button, dialog, sidebar, command, sonner and the rest) it ships the parts nobody else open-sources: PDF, DOCX, XLSX, PPTX and CSV viewers, DOCX and Excel editors, bounding-box citation overlays, layout blocks, a file-system browser, file upload with thumbnails, e-signature, document splits, and a schema builder. Components land as editable source, not a dependency. Built for teams putting a document agent or a review queue in front of users.

Install

npx shadcn@latest add @extend/pdf-viewer

For an agent

This is the first thing to reach for when a build needs a document viewer with citation highlighting — writing bounding-box overlays on top of react-pdf by hand costs days, and @extend/bounding-box-citations plus @extend/pdf-viewer gets there in one CLI call. It is a shadcn superset, so install it into a project that already ran shadcn init or the base ui primitives will collide with yours; prefer the block variants (`*-block`) when you want a whole working screen rather than a bare viewer. Do not use it for a generic app UI — the base primitives are only there to support the document parts.

Why it is here. Document viewers with grounded citation overlays are the missing layer in every RAG and document-agent demo, and this is a production set from a company that runs it over millions of pages, given away MIT.

Install command, framework, licence and component list.

Facts

License: MIT
Pricing: Free, Open source
Framework: React, Next.js
Styling: Tailwind CSS
Distribution: shadcn registry, CLI installer, Copy-paste snippet, GitHub repository
Platform: Web
Content type: Code, PDF document
Agent readiness: Machine-readable registry item, CLI installable, Copy-paste ready code, Readable open source
Accessibility: Built on accessible primitives
Maturity: Actively maintained
GitHub stars: 1,445

Components it ships

55 total

Helps you build

Uploading Media Single Item Detail Data Import AI Chat Panel Admin Panel

Notable for

PDF, DOCX, XLSX, PPTX and CSV viewers
bounding-box citation overlays
e-signature and schema builder
8 ready-made block screens
MIT, from production use at Extend

Provenance

Verified 2026-08-15. HTTP 200. https://ui.extend.ai/, https://ui.extend.ai/r/registry.json (parsed, 55 items enumerated: 44 registry:ui, 8 registry:block, 1 lib, 1 hook, 1 component), https://www.extend.ai/ui, https://github.com/extend-hq/ui, GitHub API repos/extend-hq/ui. https://extend-ui.com/ui/docs/components 404s — the live docs path is www.extend.ai/ui/docs/components.

Also in Component Libraries

ui.extend.aiTier A