massCode

A free, open-source developer workspace.

Snippets, notes, HTTP requests, calculations, drawings, and dev tools in one local-first app.
Your workspace is stored locally as plain Markdown files.

Download  |  Documentation  |  Changelog

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, HTTP requests, calculations, drawings, 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.

• Task notes with status, priority, due dates, and Today / Upcoming / Completed views
• Completed task cleanup and auto-clean scheduling
• Dashboard with activity overview, recent notes, top linked notes, and a notes graph preview
• Editor, Live Preview, and Preview modes
• Editable markdown tables with row and column controls
• Internal links to notes, snippets, and HTTP requests, with placeholders for items you plan to create later
• Note inspector with section navigation and reordering, link filters, and grouped callouts
• Fullscreen notes graph for exploring internal links between notes
• Integrated Mermaid diagrams
• Mind maps generated from markdown heading structure
• Fullscreen presentation mode for demos and meetings
• Callout blocks, including TODOs for unfinished writing, and image embedding

HTTP Client

Build and test API workflows alongside your code snippets and project notes.

• Send HTTP and GraphQL requests and exchange WebSocket messages
• Organize collections and nested folders with shared auth, headers, variables, and scripts
• Switch environments, protect tokens with local secret variables, and pass response values between requests
• Check responses with assertions and JavaScript tests, then run collections or folders in sequence
• Edit query parameters, headers, authentication, and JSON, text, form, or file payloads
• Generate request code for 20 languages and runtimes, including cURL
• Inspect responses and saved history, debug traffic in Console, and manage cookies and transport settings
• Import collections from OpenAPI, Postman, and Bruno

See the HTTP documentation to get started.

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)

Drawings

Sketch diagrams, wireframes, and whiteboard ideas on an Excalidraw-powered canvas next to your snippets and notes.

• Searchable list of drawings with keyboard navigation
• Pan and zoom remembered per drawing, with fit-to-content to recenter
• Export drawings as images
• Embed drawings directly in your markdown notes

Developer Tools

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

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

Command Palette

Jump to spaces, snippets, notes, HTTP requests, and common actions from anywhere with a keyboard-first command palette.

• Open with Cmd+P on macOS or Ctrl+P on Windows and Linux
• Search across snippets, notes, HTTP requests, spaces, and commands
• Run create actions for snippets, notes, HTTP requests, and folders
• Scope search to a space with @ or open command mode with >

Imports

Bring existing work into your vault with preview-first imports for snippets, notes, and API collections.

• Import snippets from VS Code, Raycast, SnippetsLab, and public GitHub Gists
• Import markdown notes from Obsidian folders
• Import HTTP collections from OpenAPI, Postman, and Bruno
• Review detected items, folders, tags, environments, and warnings before writing anything

Browser Clipper

Save web content from Chrome, Firefox, or Safari into the local massCode app.

• Install the Chrome version from the Chrome Web Store
• Save selected code as snippets
• Save selected text or readable page content as notes
• Save pages or links as HTTP GET requests
• Connect through the local Integration API with an API token

AI Assistant

Ask the built-in assistant to carry out tasks across Code, Notes, and HTTP using your own AI provider account or a local model.

• Edit and format snippets, organize notes, and update tasks
• Find records across your vault and use them in a conversation
• Run HTTP collections with confirmation, explain failed checks, and save reports in Notes
• Request a preview before edits, adjust a task while it runs, and undo changes that support Undo

Cloud providers receive the context used for the task; use a model running on your computer for local processing. See the AI Assistant guide for setup and examples.

MCP Integration

Connect Claude Code, Codex, Cursor, or VS Code Copilot to your massCode vault through the built-in MCP server.

• Find and read snippets, notes, and saved HTTP requests from your coding agent
• Save snippets and notes to folders with tags, and update them with protection against overwriting newer changes
• Organize folders, move items, and send them to Trash or restore them when you allow changes to existing items
• Organize and edit HTTP requests in collections
• Preview and send requests using the active massCode environment, then inspect saved execution history

See the MCP setup guide to connect your agent.

Markdown Vault

Your snippets, notes, and HTTP requests 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.

Contributions

massCode accepts external pull requests only for localizations and new syntax highlighting languages. To report a bug, please open an issue. For feature requests and ideas, start a discussion in GitHub Discussions.

See CONTRIBUTING.md for details.

Build Locally

pnpm install

pnpm build

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

pnpm dev

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License

AGPL-3.0

Copyright (c) 2019-present, Anton Reshetov.