Omnicore Markdown Viewer

A sleek, cross-platform markdown viewer with full HTML support, Mermaid diagram rendering, and powerful note-taking

What's New in v2.0.7

• Fixed - Bold and italic formatting applied incorrectly in certain cases
• Fixed - Ctrl+Z / Ctrl+Y undo and redo not working correctly in some scenarios

Features

Core Rendering

• Full HTML Support - Render HTML tags within markdown with DOMPurify sanitization
• Mermaid Diagrams - Beautiful diagram rendering with interactive popup viewer featuring pan/zoom controls
• OmniWare Wireframes - Built-in wireframe diagram support
• PrismJS Syntax Highlighting - Code blocks with Solarized Light theme (offline support for 11+ languages)
• Interactive Tables - Tabulator.js integration with sorting, filtering, pagination, and CSV/JSON export

Editing & Export

• Live Markdown Editor - Split-view editing with fast 400ms debounced preview and Fira Code font
• Tab → 2 Spaces - Tab key inserts 2 spaces in the editor for consistent indentation
• Inline Text Editing - Right-click any selected text to edit it in place with partial DOM rendering
• Undo / Redo - Ctrl+Z / Ctrl+Y undo/redo stack covering all view-mode edits
• PDF Export - One-click export with full styling, diagrams, and syntax highlighting
• Word Export - Export documents as Microsoft Word (.docx) files
• Auto-Save Detection - Unsaved changes indicator with confirmation prompts

Image Slider

Create auto-playing image carousels by wrapping images in slider tags:

• Auto-plays every 5 seconds, pauses on hover
• Navigation arrows and dot indicators with slide counter
• Click the zoom button on any slide to open it in a dedicated popup window

Auto-playing image carousel with arrow navigation, dot indicators, and per-slide zoom popup

Mermaid & Table Dialogs

Right-click anywhere in the document to insert or edit diagrams and tables without writing code manually.

• Insert Mermaid - Opens a dialog with 12 diagram templates and a live preview panel
• Edit Mermaid - Right-click any diagram to open the editor pre-filled with its source
• Delete Mermaid - Remove diagrams via right-click; source is updated without re-render
• Insert Table - Configure rows, columns, and header row with a live table preview
• Edit Table - Right-click any table to open the dialog pre-filled for editing
• Delete Table - Remove tables via right-click

Mermaid insert dialog — choose from 12 templates, edit code on the left, see the live diagram on the right

Table insert dialog — set rows, columns, and header row; preview updates instantly before inserting

Note System

Select any text and annotate it with a colored note. Notes show as highlighted underlined text with a tooltip on hover.

• Text Notes - Select any text and add colored notes with background highlight and colored underline
• Image Notes - Annotate images with notes
• Note Labels - Place floating label badges anywhere in the document
• All Notes Panel - Side panel listing all notes sorted by ID with search functionality
• Note Search - Search notes by ID or title, with auto-scroll to matching note
• Find Note - Quick note lookup via right-click context menu
• Show/Hide Notes - Toggle note visibility; when hidden, notes are completely invisible
• Edit & Delete Notes - Right-click context menu on notes for editing and deletion
• 6 Color Options - Orange, red, green, blue, purple, yellow

Notes appear as colored highlights with a tooltip showing the note title and content on hover

Right-Click Context Menu

A comprehensive context menu is available anywhere in the document with a right-click.

• Copy / Copy as Plain Text
• Edit Text - Edit selected text inline with partial DOM rendering
• Bold / Italic / Code Block / List - Quick inline formatting (DOM patch — no full page re-render)
• Remove Formatting - Strip markdown formatting from selection
• Add Note / Edit Note / Delete Note / Find Note - Full note management
• Insert Mermaid / Edit Mermaid / Delete Mermaid - Diagram management with template dialog
• Insert Table / Edit Table / Delete Table - Table management with live-preview dialog
• Insert Image / Delete Image
• Copy Code - Copy the source of a code block to clipboard
• Copy Image Source - Copy an image's src attribute to clipboard
• Select All

Right-click context menu with formatting, note management, diagram and table options

Image Zoom Popup

• Click the maximize button on any image to open it in a dedicated popup window
• Pan by clicking and dragging; zoom with the scroll wheel
• Export the current view as PNG or JPG

Navigation & UI

• Dropdown Menus - Organized File, View, and Tools dropdown menus
  • File - Open, Table of Contents, Edit Mode, All Notes, Export (PDF/Word), Recent Files
  • View - Zoom, Dark Mode, Fullscreen, Show/Hide Notes
  • Tools - Language settings (Document translation & Interface language)
• Auto Table of Contents - Hierarchical index of all headers (H1-H6) with one-click navigation
• Search with Highlighting - Real-time text search with match counter and keyboard navigation (Ctrl+F)
• File Path Display - Shows current file path with copy-to-clipboard functionality
• Instant Dark Mode - Switches theme without re-rendering the page; Mermaid SVGs are redrawn in-place

Translation & Localization

• Document Translation - Translate documents to English or Turkish via Google Translate (runs in background, non-blocking)
• Interface Language - Switch UI language between English and Turkish
• Dual-source Editing - Edit documents while viewing translations without switching back
• Resilient Translation - Per-piece fallback: if individual lines fail to translate, the rest of the document still translates

View Controls

• Dark Mode - Instant toggle between light and dark themes (Ctrl+D)
• Zoom Controls - Flexible zoom from 50% to 200% via keyboard shortcuts or mouse wheel
• Fullscreen Mode - Distraction-free viewing (F11)

Performance

• Partial DOM Rendering - Bold, italic, code, and formatting changes patch only the affected DOM node — no full page refresh
• Instant Dark Mode - Only Mermaid SVGs are redrawn on theme change; all other styling is CSS-driven
• Render Generation Guard - Stale renders are cancelled automatically when content changes rapidly
• Mermaid SVG Cache - Unchanged diagrams are restored from cache without re-running Mermaid

Additional Features

• Professional Theme - Clean interface with Omnicore branding (#279EA7 teal, #1F3244 navy)
• Cross-Platform - Works on Windows, macOS, and Linux
• Offline Support - All libraries bundled locally, no internet required (except translation)
• Single Instance - Prevents multiple app instances
• Toast Notifications - User-friendly feedback for all operations
• Recent Files - Quick access to last 100 files from File menu
• OS-Level File Watching - Instant reload when the file is modified externally (no polling delay)

Installation

Download Pre-built Releases

Download the latest release from the Releases page:

Platform	File	Description
Windows	Omnicore-Markdown-Viewer-Setup-X.X.X.exe	Windows installer
Linux	Omnicore.Markdown.Viewer-X.X.X.AppImage	Portable AppImage
Linux	omnicore-markdown-viewer_X.X.X_amd64.deb	Debian/Ubuntu package

Windows Installation Note

"Windows protected your PC" Warning

On first run, Windows SmartScreen may show a warning because the app is not code-signed.

To proceed:

1. Click "More info"
2. Click "Run anyway"

This is safe - you can verify the source code in this repository.

Build from Source

1. Install dependencies:

npm install

Running the Application

Start the application in development mode:

npm start

Building for Production

Standalone Portable EXE (No Installation Required)

npm run build

This creates a portable .exe file in dist/ folder that can run without installation.

Windows Installer (NSIS)

npm run build-installer

This creates a Windows installer in dist/ folder.

Build Both

npm run build-all

This creates both portable exe and installer.

Output location: dist/ folder

Controls

Keyboard Shortcuts

• Ctrl+O (Cmd+O on Mac) - Open markdown file
• Ctrl+S (Cmd+S on Mac) - Save file (in edit mode)
• Ctrl+Z - Undo last view-mode edit
• Ctrl+Y - Redo last view-mode edit
• Ctrl+F (Cmd+F on Mac) - Open search panel
• Ctrl+B - Bold selected text
• Ctrl+I - Italic selected text
• Ctrl+` - Code block
• Ctrl+D - Toggle dark mode
• Ctrl++ - Zoom in
• Ctrl+- - Zoom out
• Ctrl+0 - Reset zoom to 100%
• Ctrl+Enter - Confirm in Mermaid/Table dialogs and Edit Text dialog
• Enter (in search) - Next match
• Shift+Enter (in search) - Previous match
• Escape - Close search panel / Exit dialogs
• F11 - Toggle fullscreen
• Tab (in editor) - Insert 2 spaces

Mouse Controls

• Ctrl+Mouse Wheel (Cmd+Mouse Wheel on Mac) - Zoom in/out
  • Scroll up to zoom in
  • Scroll down to zoom out
• Right-click - Context menu with formatting, notes, diagrams, tables, and editing options

Search Features

• Real-time highlighting - Matches are highlighted as you type
• Match counter - Shows current match and total matches (e.g., "3 of 15")
• Navigation - Use arrow buttons or Enter/Shift+Enter to navigate
• Case-insensitive - Searches ignore case differences
• Minimum 2 characters - Search activates after typing at least 2 characters

Table of Contents

• Auto-generated - Automatically extracts all headers (H1-H6) from document
• Hierarchical display - Shows header levels with indentation
• One-click navigation - Click any header to jump to that section
• Active highlighting - Current section is highlighted in the TOC
• Accessible from File menu - Toggle via File > Table of Contents

Supported File Types

• .md - Markdown
• .markdown - Markdown
• .mdown - Markdown
• .mkd - Markdown
• .mkdn - Markdown

Opening Files

Method 1: Within the App

• Press Ctrl+O or use File > Open File
• Access recent files from File > History section

Method 2: Windows "Open With"

• Right-click any .md file in Windows Explorer
• Select "Open with" > "Omnicore Markdown Viewer"
• The file opens directly in the app

Method 3: Default Program (After Installer)

• The NSIS installer registers the app for .md files
• You can set it as the default program for markdown files
• Double-click any .md file to open in Omnicore Markdown Viewer

Mermaid Support

The viewer supports all Mermaid diagram types. Use mermaid code blocks or insert via right-click:

```mermaid
graph TD
    A[Start] --> B[Process]
    B --> C[End]
```

Right-click anywhere in the document and choose Insert Mermaid to pick from 12 built-in templates.

The slider auto-plays every 5 seconds, pauses on hover, and each slide can be opened in a zoom popup.

Technology Stack

• Electron 27.0 - Cross-platform desktop framework
• Marked - Fast markdown parser with full GFM support
• Mermaid - Diagram rendering engine (flowcharts, sequence diagrams, etc.)
• Tabulator.js 6.2.5 - Interactive table library with advanced features
• PrismJS - Syntax highlighting for code blocks (11+ languages)
• DOMPurify - XSS protection via HTML sanitization
• Fira Code - Beautiful monospace font for code editing

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

1. Fork the repository
2. Create your feature branch (git checkout -b feature/AmazingFeature)
3. Commit your changes (git commit -m 'Add some AmazingFeature')
4. Push to the branch (git push origin feature/AmazingFeature)
5. Open a Pull Request

Development

# Install dependencies
npm install

# Run in development mode
npm start

# Build for Windows
npm run build-all

License

MIT License - see the LICENSE file for details

Credits

Developed by Omnicore