Brennan's Gemini Blog

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I created a .md to .gmi converter for anyone to use.

Hi there, I made a client-side web application that converts Markdown files to Gemtext format, built with vanilla HTML, CSS, and JavaScript. Supports drag-and-drop upload, live preview, batch processing, and download.

Live demo: https://gemtext.brennan.day

https://gemtext.brennan.day

External Dependencies

This project uses minimal external resources for functionality:

marked.js v9 (CDN) — Markdown parser and lexer
Loaded from https://cdn.jsdelivr.net/npm/marked@9/marked.min.js
Used to parse Markdown tokens for conversion to Gemtext
License: MIT

JSZip v3 (CDN) — ZIP file creation library
Loaded from https://cdn.jsdelivr.net/npm/jszip@3/dist/jszip.min.js
Used for batch download functionality
License: MIT or GPLv3

Font Awesome 7.2.0 (CDN) — Icon library for UI elements
Loaded from https://cdn.jsdelivr.net/npm/@fortawesome/fontawesome-free@7.2.0/css/all.min.css
Used for all interface icons (upload, settings, download, etc.)
License: CC BY 4.0 (Font Awesome) / CC BY-SA 4.0 (Font Awesome Free)

Overview

Gemtext is the native text format for the Gemini protocol, a simpler alternative to the web. This converter transforms standard Markdown into clean Gemtext while preserving essential structure and links.

No server processing, everything runs in your browser
Your files never leave your device
Works offline once loaded
Open source and privacy-focused

Features

Drag-and-drop upload of .md, .markdown, and .txt files
Live preview with rendered and raw Gemtext views
Batch processing with ZIP download
Settings modal for conversion options
Responsive design for mobile and desktop
Accessibility with ARIA labels and keyboard navigation

Usage

Open https://gemtext.brennan.day in your browser

https://gemtext.brennan.day

Drag Markdown files onto the drop zone or click to select files
View the converted Gemtext in the preview pane
Toggle between rendered and raw views
Download individual .gmi files or a ZIP archive of all files
Adjust settings in the gear menu for different conversion behaviors

Conversion Rules

Headings H4–H6 are downgraded to H3 (###)
Inline links are extracted to => URL text lines
Ordered lists become unordered (*)
Nested lists are flattened with indentation
Tables become preformatted blocks
Images become => URL alt-text links
Bold, italic, strikethrough, and inline code are stripped
HTML tags are removed; entities are decoded
Code blocks are preserved with language tags

Settings

Link placement: After paragraphs or at document end
Heading downgrade: Limit headings to level 3
Table conversion: Preformat or skip
List flattening: Flatten nested lists with indentation
Image handling: Convert to links or skip
Frontmatter: Strip or render as preformatted
Line endings: LF or CRLF
Source comments: Add conversion metadata

Development

Local Development

# Serve the project locally
python3 -m http.server 8765
# or
npx serve .

Then visit http://localhost:8765

http://localhost:8765

Project Structure

markdown2gemtext/
├── index.html              # Main SPA
├── css/
│   ├── main.css            # Core styles and dark theme
│   ├── preview.css           # Gemtext preview styling
│   └── responsive.css      # Mobile layout
├── js/
│   ├── converter.js        # Markdown → Gemtext conversion
│   ├── fileHandler.js      # File loading and downloads
│   ├── preview.js          # Preview rendering
│   └── app.js              # Main application orchestration
├── test/                   # Test cases and expected outputs
└── docs/
    └── SPEC.md             # Technical specification

Testing

The test/ directory contains edge-case Markdown files and their expected Gemtext outputs. Use these to verify conversion correctness:

# Compare actual vs expected outputs
diff test/expected/*.gmi test/actual/*.gmi

Deployment

The app is designed for static hosting. Netlify configuration is included:

netlify.toml — SPA routing and build settings
No build step required — just deploy the files as-is

Privacy and Security

All processing happens client-side in your browser
No files are transmitted to any server
No analytics or tracking
No cookies or local storage beyond settings persistence
Works offline after initial page load

Browser Support

Modern browsers with ES6+ support
Tested in Chrome, Firefox, Safari, Edge
Mobile browsers supported

About

A 🍓 Berry House project by Brennan Kenneth Brown.

Berry House
Brennan Kenneth Brown

License

AGPL 3.0

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