FREE & OPEN SOURCE · LOCAL-FIRST · WORKS OFFLINE

Your developer
workspace.

Code, notes, APIs, diagrams, and calculations.
Always within reach.

Download Free Explore workspaces

Install via Homebrew

brew install --cask masscode

Code snippets organized in folders with a TypeScript snippet open in the editor

Markdown notes with a folder library and note editor

HTTP client with saved requests, request configuration, and response panel

Excalidraw canvas in the Drawings workspace

Organize snippets in folders, use tags, and keep useful code within reach.

Explore Code snippets

Also built in Math notebook Developer tools

LESS SCATTERED. MORE CONNECTED.

From saved knowledge
to working solutions.

CONNECTED KNOWLEDGE

See how your ideas connect.

Explore the links between your notes in a graph. Connect technical notes to the snippets and API requests they explain, so the next step is always close.

Explore Notes

Notes Graph showing connections between linked notes

TASK NOTES

Turn your notes into next steps.

Track tasks with status, priority, and due dates. Link to planned notes, snippets, and API requests. Keep context close and find tasks by due date in Today and Upcoming.

Explore Notes

Task note with status, priority, and due date

API WORKFLOWS

Test the whole flow.

Run saved requests in sequence, pass values between steps, and inspect test results. Follow a workflow from login to its final response and see where it fails.

Explore the HTTP client

HTTP request with assertions and passing test results

COMMAND PALETTE

A few keystrokes away.

Find snippets, notes, and requests from anywhere in massCode. Switch spaces, create something new, or run a command—all from your keyboard.

Meet the Command Palette

⌘ P to search · ⌘ ⇧ P for commands

Command Palette search with recent items and actions

BUILT-IN AI ASSISTANT

From a question to a finished task.

Ask massCode to edit code, organize notes, or work through an HTTP workflow. Find what you need in your vault and put it to work in the same conversation.

Edit your code

Update snippets and fragments using the code you have open.

Add a five-second timeout to this function and update the usage example.

Organize your notes

Find records, rewrite notes, and update task properties across your vault.

Find overdue tasks and move them to Follow-up.

Test your APIs

Add checks, run collections with your confirmation, and investigate failed requests.

Run this collection, explain the failed checks, and save a report in Notes.

Your choice of model.

Connect OpenAI, Anthropic, Gemini, DeepSeek, Mistral, or xAI with your own API key. Or use a model running on your computer with Ollama or LM Studio. Cloud API usage is billed by your provider.

Apply changes or preview first.

Have the assistant make edits directly, or ask for a preview first. Sending HTTP requests requires your confirmation.

Get started with AI Assistant

Connect your external AI agent.

Already working in an AI client? Let it find saved snippets, read project notes, and run HTTP requests through MCP.

Bring your saved context into the conversation.

Reuse what you already know. Save the next useful solution back to massCode.

Connect your agent

The little tools you reach for.

Compare a response. Convert a value. Work out a number.
Keep the small tasks in the same workspace.

Spot the difference.

Compare JSON side by side and inspect nested changes. Then reach for encoders, converters, and generators when you need them.

Explore developer tools

JSON Diff comparing original and modified JSON side by side

Keep the calculation.

Use variables, convert units and currencies, and see results as you type. Keep the steps behind a number in your Math Notebook.

Explore Math Notebook

$Math Notebook with variables, percentages, currency and unit conversions$

Your work. On your machine.

Keep your whole workspace close. Local files, open formats, and control over how your work moves between devices.

My workspace vault

code

notes

http

Northstar Commerce

Read an echo.md

math

Plain files. Yours to keep.

Code, notes, and requests in Markdown. Drawings in Excalidraw. Open your files outside massCode, too.

How storage works

My workspace

iCloudDropboxSyncthingGit

Your sync. Your choice.

Keep your vault on one computer, or sync its folder using iCloud, Dropbox, other cloud storage, Syncthing, or Git.

Explore sync options

Make room for your next idea.

Keep the code, context, and tools you need in one place. Free, open source, and ready to work offline.

Download Free

Bringing snippets, notes, or API collections from another app? Explore import options

Your developerworkspace.