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April 2026 — 6 min read

Free ERD Tool Online — Visual Entity Relationship Diagram Editor

A free ERD tool lets you sketch a database structure before writing a single line of SQL. This guide covers what to look for in an online ER diagram editor, the difference between generic and SQL-aware tools, and how to use SQL Designer — a completely free ERD tool — to go from blank canvas to exported SQL script.

What Is an ERD Tool?

An ERD tool (entity relationship diagram tool) is software for drawing entity-relationship diagrams — the standard way to visualise a relational database schema. Each entity (table) is drawn as a rectangle with its attributes (columns) listed inside. Lines connecting entities represent relationships, with notation on each end showing cardinality: one-to-one, one-to-many, or many-to-many.

ERD tools range from generic diagram editors (draw.io, Lucidchart) to SQL-aware tools that understand database types and can generate DDL scripts. For database design work, a SQL-aware tool is almost always the better choice.

Free vs. Paid ERD Tools

Many popular ERD tools are partially free: they offer a free tier that is limited by the number of diagrams, the number of objects per diagram, or export capabilities. Common restrictions include:

• SQL export locked behind a paid plan
• Private diagrams requiring a subscription
• Diagram count limits on free accounts
• Watermarks on exported images

A genuinely free ERD tool has no diagram limits, no export paywalls, and no credit card required to get started. SQL Designer is one of them — completely free, with unlimited diagrams and full SQL export.

What to Look for in an Online ERD Tool

The best free ERD tools for database design share a few key characteristics:

• SQL-aware column types — understand INT, VARCHAR, DECIMAL, TIMESTAMP and other real database types, not just generic boxes
• Constraint support — PRIMARY KEY, UNIQUE, NOT NULL, AUTO_INCREMENT / SERIAL
• Visual foreign key relationships — draw lines between tables to define FK references
• SQL export — generate a valid CREATE TABLE script from the diagram
• Crow's foot notation — the standard cardinality notation used by most databases and teams
• Auto-save — changes saved without manual action
• No install required — runs in the browser, available from any device

SQL Designer — Free ERD Tool for MySQL and PostgreSQL

SQL Designer is a free online ERD tool built specifically for relational database schema design. It supports both MySQL and PostgreSQL, with type-specific column pickers for each. The drag-and-drop canvas lets you add tables, define columns with the correct types and constraints, and connect tables with foreign key lines — all visually, without writing any SQL manually.

When the diagram is complete, click Export to generate a CREATE TABLE script for MySQL or PostgreSQL. The exported SQL includes all column definitions, data types, constraints, and foreign key declarations — ready to run in your database.

There are no diagram limits, no SQL export paywalls, and no subscription. Create a free account with your email and you can start immediately. Diagrams are saved to your account and accessible from any device.

How to Use SQL Designer as a Free ERD Tool

• 1. Create a diagram — sign up for free and create a new diagram for your project or database.
• 2. Add tables — click the canvas to add a table entity and give it a name.
• 3. Define columns — add columns with names, data types (MySQL or PostgreSQL), and constraints (PK, UQ, NN).
• 4. Draw relationships — drag a connection from a foreign key column to the primary key on the referenced table. Crow's foot notation is applied automatically.
• 5. Export SQL — generate a complete CREATE TABLE DDL script for MySQL or PostgreSQL in one click.

ERD Tool vs. Generic Diagram Tool

Generic tools like draw.io are useful for high-level conceptual diagrams to share with non-technical stakeholders. They let you draw any shape you like, but they don't understand SQL. If you rename a column in a generic tool, nothing in the output changes — because there is no output.

A dedicated free ERD tool like SQL Designer keeps the diagram and the SQL in sync. Every constraint and data type you define in the visual editor appears correctly in the exported script. That makes it the right tool when you're designing a schema that will actually be implemented.