Firefox Extension

May 26, 2026 · View on GitHub

Markdown Viewer is available for Firefox with full feature support.

Overview

Feature	Status
Markdown rendering	✅
Word export	✅
All diagram types	✅
LaTeX formulas	✅
29 themes	✅
Smart caching	✅
Offline mode	✅

Version: 5.0.0
Manifest: V3
Minimum Firefox: 140.0

Installation

From Firefox Add-ons

Visit Firefox Add-ons - Markdown Viewer
Click "Add to Firefox"
Confirm the installation

Manual Installation (For Developers)

Clone the repository
Run npm install && npm run build:firefox
Open about:debugging
Click "This Firefox"
Click "Load Temporary Add-on"
Select any file in the firefox/dist folder

Firefox-Specific Features

Background Page

Unlike Chrome's service worker, Firefox uses a background page for better compatibility with WebAssembly-based renderers.

WebRequest Handling

Firefox version includes webRequest and webRequestBlocking permissions for more reliable file type detection.

Permissions Explained

Permission	Purpose
`storage`	Save settings and cache
`unlimitedStorage`	Store diagram cache
`downloads`	Save Word exports
`tabs`	Detect markdown files
`activeTab`	Process current tab
`scripting`	Inject rendering scripts
`webRequest`	Detect file types
`file:///*`	Access local files
`https:///`, `http:///`	Access online files

Supported File Types

Firefox follows the same shared format registry as the Chrome and Edge builds:

Extensions	Type
`.md`, `.markdown`, `.slides.md`	Markdown / Slidev documents
`.plantuml`, `.puml`	PlantUML diagrams
`.mermaid`, `.mmd`	Mermaid diagrams
`.vega`, `.vl`, `.vega-lite`	Vega / Vega-Lite charts
`.gv`, `.dot`	Graphviz DOT graphs
`.infographic`	Infographic charts
`.canvas`	Canvas diagrams
`.drawio`	draw.io diagrams

File Access Setup

To open local Markdown files:

Go to about:addons
Find Markdown Viewer
Click the extension name
Under Permissions, enable file access

Known Differences from Chrome

Feature	Chrome	Firefox
Background	Service Worker	Background Page
Offscreen API	Used	Not available (alternative used)
Performance	Slightly faster	Comparable

Both versions provide the same user-facing features.

Keyboard Shortcuts

Action	Shortcut
Export to Word	`Ctrl + S` / `Cmd + S`
Toggle TOC	`Ctrl + B` / `Cmd + B`
Zoom in	`Ctrl + +` / `Cmd + +`
Zoom out	`Ctrl + -` / `Cmd + -`
Reset zoom	`Ctrl + 0` / `Cmd + 0`

Troubleshooting

Extension Not Loading?

Check Firefox version (requires 140.0+)
Verify extension is enabled in about:addons
Try disabling and re-enabling
Restart Firefox

Local Files Not Opening?

Go to about:addons
Find Markdown Viewer → Permissions
Ensure file access is enabled

Diagrams Not Rendering?

Check browser console for errors
Verify diagram syntax is correct
Try clearing cache and reloading

Development

Build for Firefox

npm install
npm run build:firefox

Test in Firefox

# Load in about:debugging
# Or use web-ext:
web-ext run --source-dir firefox/dist

Firefox-Specific Code

Firefox-specific implementations are in the firefox/ directory:

manifest.json — Firefox-specific manifest
src/host/ — Background page implementation
src/webview/ — Firefox-optimized rendering

Privacy & Security

✅ All processing local
✅ No external requests
✅ No tracking
✅ Open source

Same privacy guarantees as the Chrome version.

Source Code

GitHub: markdown-viewer-extension

Firefox-specific code is in the firefox/ directory.