macgramDraw your data model in a few clicks
Place your entities, link them, and the logical model is written beneath the diagram as you draw. macgram is a free conceptual data model editor (Merise / UML), in the browser, on Windows and on Linux.
Desktop app, free
Install macgram on your computer
Everything the online editor does, plus:
- The AI assistant: Claude Code or Codex draw your diagram live
- Your files opened and saved straight on your disk
- The diagram reloads when the file changes, handy with git
- Updates install themselves
Download macgram one last time
Version 0.4.2 and earlier cannot update themselves. Install the new version over it: later versions will offer each update on their own.
Rather not install anything? Open the editorAll versions
Your first diagram in a minute
No account to create, nothing to install: the editor opens in your browser.
- 1
Place your entities
Pick the Entity tool (E) and click the canvas. Double-click an entity to name it and add its attributes.
- 2
Link them
Click two entities: the association appears between them. Click a link to change its cardinality.
- 3
Read the logical model
The relational model is written under the diagram as you go, primary and foreign keys included.
- 4
Save or export
Keep your diagram in a .mcd.json file, or export it as PNG or SVG for your report.
What the editor does
- Merise and UML
- Entities, binary, n-ary or standalone associations, cardinalities, enums, notes and annotation arrows.
- AI assistant
- In the desktop app, ask Claude Code or Codex for a diagram or a change: the AI draws live, and Ctrl+Z undoes each of its actions.
- Automatic layout
- Rearranges the diagram to limit link crossings.
- PNG and SVG export
- True to the current theme, with enums as a legend.
- Looping import
- Your .loo files open as a macgram diagram; rules become notes.
- Keyboard first
- E, R and T for the tools, Ctrl+F to find an element, Ctrl+D to duplicate, Ctrl+Z to undo.
- Made for git
- A readable JSON file, one element per line: clean diffs and merges without conflicts.
- Built-in updates
- The desktop app tells you about each new version and installs it if you want.
Coming soon: your macgram account
Accounts are on their way, so your diagrams follow you and can be worked on together.
- Your diagrams online
- Open them from any device, without carrying files around.
- Shared files
- Share a diagram with your project group or your teacher instead of emailing it around.
Frequently asked questions
What is a conceptual data model (MCD)?
The conceptual model of the Merise method: entities, their attributes and the associations between them, with cardinalities. macgram derives the logical relational model (MLD) from it.
Is macgram free?
Yes, for everyone, companies included. Its licence (MIT with Commons Clause) only forbids selling macgram, or a product or service that derives most of its value from it.
Are my diagrams sent to a server?
No. The editor runs in your browser or on your computer, and your diagrams stay in files on your device.
How does the AI assistant work?
In the desktop app, macgram runs the Claude Code or Codex already installed on your machine, with your own account: no key to enter. The AI only acts on the open diagram, with no access to your files or your terminal. The web version has no assistant.
Can I bring my Looping diagrams?
Yes: open the .loo file with Ctrl+O and it is imported as a new diagram. Attribute types are not carried over.
Which systems does macgram run on?
Any recent browser, Windows (installer or portable zip) and Linux (AppImage for every distribution, .deb for Debian, Ubuntu and Mint, .rpm for Fedora, or a .tar.gz archive). There is no macOS download yet.