massCode

A free, open-source developer workspace.

Snippets, notes, calculations, and dev tools in one local-first app.
Your data stays on your machine as plain Markdown files.

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Extensions: VS Code | Raycast

_{Available for macOS, Windows, and Linux}

Support

massCode is free and open source. But building and maintaining a quality tool takes time. Your support helps keep development going and new features coming.

SPONSORS

 

About

Originally a snippet manager, massCode now brings together snippets, notes, calculations, and developer tools in one desktop app, so everyday work stays in one place.

Features

Code Snippets

Use massCode as a focused snippet workspace with multi-level folders, tags, and fragments for organizing reusable code across projects and languages.

• 160+ syntax grammars out of the box (600+ supported via .tmLanguage)
• Integrated Prettier for code formatting
• Real-time HTML & CSS preview for quick prototyping
• JSON Visualizer for exploring nested structures as interactive graphs
• Export snippets as polished images with customizable themes

Notes

Write longer markdown documents right next to your snippets: project docs, drafts, research notes, and personal knowledge bases.

• Editor, Live Preview, and Preview modes
• Integrated Mermaid diagrams
• Mind maps generated from markdown heading structure
• Fullscreen presentation mode for demos and meetings
• Callout blocks and image embedding

Math Notebook

A calculator-style notebook for natural-language calculations, conversions, and date math without leaving your workflow.

• Arithmetic, percentages, unit conversions, and date/time math
• 166+ fiat currencies, 21 cryptocurrencies with live exchange rates
• Variables, functions, and aggregates for quick iterative calculations
• Finance calculations (compound interest, ROI, loan repayment)

Developer Tools

Built-in utilities for the small tasks that usually send you to a browser tab:

• Text: Case Converter, Slug Generator, URL Parser
• Crypto: Hash/HMAC Generator, Password Generator, UUID
• Encoders: URL, Base64, JSON to TOML/XML/YAML, Color Converter
• Generators: JSON Generator, Lorem Ipsum

Markdown Vault

Your snippets and notes live as plain .md files on disk with frontmatter metadata, so the data stays readable and portable.

• Git-friendly - track changes and sync via any Git remote
• Cloud sync - works with iCloud, Dropbox, Google Drive, Syncthing
• Live sync - massCode watches the vault and picks up external changes in real time
• No vendor lock-in - your data is always yours

Custom Themes

Customize the app UI and editor syntax highlighting with JSON theme files. Supports light and dark themes with live reload. See the theme docs.

Build Locally

Instructions for building from source

Prerequisites

• Node.js (>=20.16.0)
• pnpm (>= 9.0.0)

Install Dependencies

pnpm install

Build

To build for current platform:

pnpm build

To build for a specific platform:

pnpm build:mac    # macOS
pnpm build:win    # Windows
pnpm build:linux  # Linux

Development

To run in development mode:

pnpm dev

Troubleshooting

macOS: "massCode is damaged and can't be opened"

This is caused by macOS security settings. Fix it with:

Option 1: System Settings (macOS 13+)

1. Open System Settings -> Privacy & Security
2. Find "massCode" and click Allow Anyway

Option 2: Terminal

sudo xattr -r -d com.apple.quarantine /Applications/massCode.app

Follow

• News and updates on X
• Discussions

License

AGPL-3.0

Copyright (c) 2019-present, Anton Reshetov.