Lumen Reader

A beautiful, modern Markdown, PDF, and CSV reader for Visual Studio Code.

Lumen turns project documents into calm, polished reading experiences without sending files anywhere or hiding the source editor. Read Markdown with live synchronization, explore PDFs with familiar navigation, and inspect CSV data in a fast virtualized grid—all with the same typography and light, dark, and sepia design.

Why Lumen?

VS Code can open many document formats, but long-form reading and data inspection deserve interfaces designed for focus. Lumen provides one recognizable reader while preserving ordinary files and familiar editor workflows.

Beautiful light, dark, and warm sepia themes
Inter, Geist, Manrope, Source Serif 4, and system typefaces
Per-document reading positions restored after restarting VS Code
Responsive navigation, keyboard-friendly controls, and in-document search
Local processing with no telemetry, analytics, accounts, or cloud upload

Markdown

Instant live preview as .md and .markdown source changes
Block-aware two-way scroll sync between source and reader
Responsive heading outline with active-section tracking
Mermaid diagrams with pan, zoom, fullscreen, reset, and source copy
KaTeX math and Shiki syntax highlighting
GFM tables, task lists, footnotes, callouts, and YAML frontmatter
Local images, workspace-relative links, and Markdown-to-Markdown navigation

PDF

Continuous page reading with lazy rendering
Page thumbnails and document outline navigation
Full-document search, page jump, zoom, fit-width, fit-page, and rotation
Selectable text, copy support, internal destinations, and safe external links
Password prompts for protected PDFs without storing the password
Original PDF page colors surrounded by Lumen's themed reader interface

CSV

Worker-backed parsing that keeps the reader responsive
Virtualized rows and columns for large project datasets
Sticky headers, row numbers, resizable columns, sorting, and per-column filters
Global search and rectangular selection copied as TSV
Automatic comma, tab, semicolon, and pipe detection with manual override
Quoted fields, embedded newlines, UTF-8, and BOM-detected UTF-16
Instant refresh from unsaved source edits when the reader is open beside the CSV

Quick start

Install Lumen Reader from the VS Code Marketplace.
Open a PDF normally; Lumen is its default VS Code reader.
For Markdown or CSV, use the reader icon in the editor title or select Open With → Lumen.
Use Lumen Reader: Open Reader to Side to keep Markdown or CSV source and reader visible together.
Choose Edit Source at any time to return to the normal text editor.

You can also install Lumen from a terminal:

code --install-extension mkpvishnu.lumen-markdown

Markdown source synchronization

In side-by-side mode, scrolling Markdown source moves the reader to the matching rendered block. Moving the cursor follows the exact source line, while scrolling the reader keeps the source nearby without stealing keyboard focus.

Double-click a rendered heading, paragraph, list, table, code block, equation, or Mermaid diagram to open its source line. Lumen remembers recent positions for up to 200 documents in the current workspace.

Mermaid diagrams use ordinary fenced blocks:

```mermaid
flowchart LR
  Source --> Reader --> Focus
```

Lumen supports classic Mermaid syntax and current Mermaid 11 diagram types. Inline math uses $...$ ; display math uses $$...$$.

CSV safety limits

Lumen warns before loading CSV files larger than 50 MiB and safely refuses files larger than 200 MiB. Rows are parsed away from the UI thread, and only a small visible window is rendered in the document. Multi-gigabyte, disk-indexed datasets are intentionally outside Lumen's scope.

Sorting, searching, filtering, column resizing, and selection only change the reader view. Lumen never rewrites CSV source from the grid.

Reading preferences

Use the Aa menu in Markdown or VS Code's Settings → Lumen Reader to change the shared theme, typeface, and text size. Existing lumenMarkdown.* setting names remain supported so upgrades preserve current preferences.

Setting	Default	Purpose
`lumenMarkdown.theme`	`auto`	Follow VS Code or use light, dark, or sepia
`lumenMarkdown.fontFamily`	`inter`	Choose a bundled or system typeface
`lumenMarkdown.fontSize`	`16`	Set body size from 13–24px
`lumenMarkdown.contentWidth`	`860`	Set Markdown reading width from 640–1400px
`lumenMarkdown.showOutline`	`true`	Show the Markdown heading outline
`lumenMarkdown.remoteImages`	`trusted`	Control HTTPS images in Markdown
`lumenMarkdown.wrapCode`	`false`	Wrap long Markdown code lines

Privacy and security

Your documents stay local. Lumen does not include telemetry, analytics, accounts, or cloud processing.

Markdown HTML is sanitized, Mermaid uses strict security mode, remote images respect workspace trust, and every webview uses a restrictive Content Security Policy. PDF and CSV workers are bundled with the extension. Unsafe link schemes are blocked, and PDF passwords are never persisted.

Support

Questions and feedback are welcome through the Q&A section on the Visual Studio Marketplace listing.

License

Lumen Reader is free and distributed under the MIT License. Bundled open-source dependency notices are included in THIRD_PARTY_NOTICES.md.