Entity Relationship Diagram Designer

ERD Designer is a free, open-source tool for visually designing database schemas.
Design your tables and relationships in the browser, VSCode, or Google Drive
— with AI integration via an agent plugin (CLI + skill) or MCP (Model Context Protocol).

Inspired by ERMaster, built for the modern development workflow.

▶ Try it now — kajitiluna.github.io/erd-designer

No installation, no account. Your diagrams stay in your browser.

Why ERD Designer?

• Design on a canvas, not in a config file — drag-and-drop tables, click-to-connect relationships,
  and instant DDL — no YAML or hand-written SQL to start.
• Your coding agent can edit it too — the diagram is not a dead-end artifact.
  Claude Code and other agents create tables, add columns, wire up relations, and generate DDL through
  the same tool catalog the app itself uses.
• Output your team actually needs — DDL for 7 databases, plus Excel / Google Spreadsheet
  specification documents and PNG / SVG / interactive HTML diagrams.
• Reviewable in Git — .erd is plain JSON, so schema changes show up as a readable diff
  in pull requests instead of an opaque binary blob.
• Define a column once, reuse it everywhere — Column Share Models and Column Groups keep
  created_at, tenant keys, and audit columns consistent across every table that uses them.

Features

Visual Database Design

• Drag-and-drop table design — Create and arrange tables, define columns, and set constraints on an interactive canvas
• Relationship management — Define 1:1 and 1:N relationships visually with automatic foreign key synchronization
• Perspectives — Organize large schemas into multiple views (e.g., by module or feature) for better manageability
• Memo notes — Add foreground/background memo notes to annotate your design

AI Agent Integration

• Agent plugin (CLI + skill) — A plugin with a bundled CLI lets coding agents edit .erd files directly,
  without a running app or MCP server. Works with Claude Code
  and GitHub Copilot CLI.
  Token-efficient: nothing is loaded into the agent context until the skill is used
• MCP Server — The VSCode extension includes a built-in
  Model Context Protocol server, enabling AI assistants like Claude
  to read and modify your ER diagrams programmatically
• One tool catalog, both surfaces — the MCP server and the CLI expose the same set of agent tools
  (add tables and columns, create relations, manage indexes and constraints, arrange the canvas, export DDL),
  so behavior never diverges between them

The agent plugin and the MCP server are still marked experimental — their tool surface may
change between releases. The visual editing features are stable.

Column Reuse & Sharing

• Column Share Model — Define a column once, reuse it across multiple tables. Type changes propagate automatically
• Column Groups — Bundle commonly used columns (e.g., created_at, updated_at) and apply them to tables in bulk

Import & Export

• DDL export — Generate CREATE TABLE scripts for PostgreSQL, MySQL, MariaDB, MS SQL Server, SQLite, BigQuery, and Snowflake
• DDL import — Import existing DDL scripts to auto-generate ER diagrams
• Specification documents — Export table definitions as Excel files or Google Spreadsheets
• Image export — Export as PNG, SVG, or interactive HTML with pan/zoom and perspective switching

Multi-Platform

Screenshots

Main canvas view with tables and relationships

Editing table columns using shared models	Creating relationships between tables

Customizing table and memo colors	Organizing tables by perspectives

Supported Databases

• PostgreSQL — Schema support, array types, GIN/GiST/BRIN indexes
• MySQL — CHARACTER SET / COLLATE, FULLTEXT / SPATIAL indexes, Auto Increment
• MariaDB — MySQL-compatible DDL, UUID / INET4 / INET6 types, Auto Increment
• MS SQL Server — Schema support, clustered indexes, Identity columns
• SQLite — Type affinity based column types, rowid-based auto numbering (table-level PRIMARY KEY), comments as -- lines, foreign keys emitted as guidance comments
• BigQuery — Dataset (schema) support, ARRAY<T> / STRUCT types, NOT ENFORCED primary / foreign keys, OPTIONS(description=...) comments
• Snowflake — Schema support, inline COMMENT syntax, AUTOINCREMENT, semi-structured types (VARIANT / OBJECT / ARRAY)

PostgreSQL/MySQL-compatible databases such as Amazon Aurora, CockroachDB, and TiDB can generally be modeled using the corresponding dialect.

Getting Started

Online Tool

Try ERD Designer instantly at kajitiluna.github.io/erd-designer
— no installation or account required. Your data is stored locally in your browser (IndexedDB).

Google Drive App

Install from the Google Workspace Marketplace
to save and edit ERD files on Google Drive.
Shared files can be viewed simultaneously, though simultaneous editing is not supported (optimistic concurrency control).

VSCode Extension

Install from the Visual Studio Marketplace
to design ER diagrams within VSCode. Save as .erd files and manage them with Git.

[!NOTE]
The MCP Server feature is currently experimental and under active development.
Functionality and behavior may change in future releases.

AI Agent Integration (agent plugin)

Let a coding agent design tables incrementally by editing .erd files directly — no MCP server or running app required.

With Claude Code:

claude plugin marketplace add kajitiluna/erd-designer
claude plugin install erd-designer@erd-designer

With GitHub Copilot CLI:

copilot plugin marketplace add kajitiluna/erd-designer
copilot plugin install erd-designer@erd-designer

The plugin ships a skill and a self-contained CLI (agent-plugin/skills/erd-designer/scripts/erd-cli.cjs, requires Node.js 20+),
so the agent consumes almost no context until the skill is actually used.
The skill folder follows the open Agent Skills format, so other skill-compatible agents may also use it.
Files stored on Google Drive can be edited through the local path synced by
Google Drive for Desktop,
with the limitation described below.

[!TIP]
(Google Drive app):
Enable "Sync Google Drive" in the gear menu to auto-detect external changes (e.g. CLI edits)
and pull them into the canvas within about 10 seconds, as an undoable edit.
This is off by default — while off, close the tab before editing via CLI, then reopen it afterward to see the result.

[!NOTE]
The agent plugin is experimental, like the MCP Server.

Manual

Please refer to the Wiki for detailed documentation.

Sample file

You can use the sample ERD file as a reference for your designs:

• sample-ec_mysql.erd
  (Right-click and select "Save link as...")

How to use:

• Online Tool: Download the file and import it into ERD Designer
• Google Drive App / VSCode Extension: Open the downloaded file directly

Installation and Usage

Local Installation

1. Clone the repository:

   git clone https://github.com/kajitiluna/erd-designer.git
   

2. Install dependencies:

   npm ci
   

3. Start the development server:

   npm run dev
   

Usage

After starting the development server, open your browser and navigate to http://localhost:5173/erd-designer to use the application.

Development

• Node.js Requirement: Ensure you have Node.js (version 22.12 or higher) installed.
• Build the Project:

  npm run build
  

• Run Tests:

  npm run testrun
  

Contributing

Contributions are welcome! See CONTRIBUTING.md for how to set up the
project, what the review expects, and how to add a new agent tool.

• Bug reports and feature requests — open an Issue
• Questions and ideas — start a Discussion
• Pull requests — please open an issue first to discuss significant changes

This project follows a Code of Conduct.
To report a security issue, see SECURITY.md.

License

ERD Designer is distributed under the Apache License 2.0.