HashMark

Note: This repository is a fork of antonmedv/textarea.

A zero-dependency, serverless Markdown editor that lives entirely in your URL. Write, preview, and share documents by simply sending a link -- no database, no accounts, no servers required.

Live Demo: danielcregg.github.io/hashmark

Overview

HashMark is a feature-rich Markdown editor that runs entirely in the browser. It encodes your document into the URL hash using deflate compression, enabling you to share complete documents as links. It supports GitHub-Flavored Markdown, Mermaid diagrams, KaTeX math equations, syntax highlighting for 180+ languages, and multiple themes.

Features

• Full GFM Markdown -- Complete GitHub-Flavored Markdown support with live preview
• Three View Modes -- Edit, Split, or Preview mode for flexible editing
• URL-Based Storage -- Documents encoded in the URL hash using deflate compression
• Mermaid Diagrams -- Eight diagram templates including flowcharts, sequence, class, state, ER, Gantt, pie, and mind maps
• Math Equations -- KaTeX rendering for inline ($...$) and block ($$...$$) math
• Syntax Highlighting -- Highlight.js support for 180+ languages with code block templates for 16 popular languages
• Three Themes -- Light, Dark, and Sepia themes that persist across sessions
• Formatting Toolbar -- Sidebar with bold, italic, headings, lists, tables, images, blockquotes, and more
• Keyboard Shortcuts -- Ctrl+B (bold), Ctrl+I (italic), Ctrl+K (link), Ctrl+Z/Y (undo/redo), Tab (indent)
• Smart Editing -- Auto-closing pairs, smart list continuation, block indent/dedent
• QR Code Sharing -- Generate QR codes for mobile sharing
• Export Options -- Download as .md, copy as HTML, or print/export to PDF
• Dual Persistence -- Stored in both localStorage and URL hash
• Emoji Shortcodes -- :smile:, :rocket:, :fire:, and more

Prerequisites

• A modern web browser with JavaScript enabled
• No installation, server, or build tools required

Getting Started

Installation

No installation is needed. HashMark is a single-file static application.

To self-host, clone the repository and serve index.html:

git clone https://github.com/danielcregg/hashmark.git
cd hashmark
# Serve with any static file server, e.g.:
python -m http.server 8000

Alternatively, deploy directly to GitHub Pages.

Usage

1. Open the editor at danielcregg.github.io/hashmark
2. Write your Markdown in the editor pane
3. Toggle between Edit, Split, or Preview modes
4. Share by clicking the Share button or generating a QR code
5. Export as .md, HTML, or PDF

Keyboard Shortcuts:

Shortcut	Action
Ctrl+B	Bold
Ctrl+I	Italic
Ctrl+K	Insert link
Ctrl+S	Save
Ctrl+Z	Undo
Ctrl+Y	Redo
Tab	Insert 2 spaces
F11	Toggle fullscreen

Tech Stack

Technology	Purpose
JavaScript	Core application logic
HTML5	Single-file application structure
CSS3	Theming and responsive layout
Marked.js	Markdown parsing (v11.1.1)
Highlight.js	Syntax highlighting (v11.9.0)
KaTeX	Math equation rendering (v0.16.9)
Mermaid	Diagram rendering (v10, lazy-loaded)
QRious	QR code generation (v4.0.2)
CompressionStream	Native deflate compression for URL encoding
GitHub Pages	Static hosting

License

This project is licensed under the MIT License. See the LICENSE file for details.