Free ER Diagram Maker Online
Free ER Diagram Maker Online
Design database schemas with entities, attributes, and relationships using Mermaid syntax.
What is a ER Diagram?
An Entity-Relationship (ER) diagram is a visual representation of a database structure. It shows entities (tables), their attributes (columns), and the relationships between them. ER diagrams are essential for database design, helping teams plan schema architecture before implementation.
Common Use Cases
- •Database design - Plan table structures and relationships
- •Data modeling - Map business concepts to database entities
- •Documentation - Communicate schema to developers and stakeholders
- •Migration planning - Visualize existing databases for refactoring
- •API design - Define data models for REST or GraphQL APIs
Syntax Quick Reference
| Element | Syntax | Description |
|---|---|---|
| Entity | ENTITY { } | Define a table |
| Attribute | type name | Column with data type |
| Primary Key | type name PK | Primary key column |
| One-to-many | ||--o{ | One to zero or more |
| One-to-one | ||--|| | Exactly one to one |
| Many-to-many | }o--o{ | Zero or more to zero or more |
Export Options
PNG Export
High-resolution images for documents and presentations.
SVG Export
Scalable vectors for web and further editing.
PDF Export
Print-ready format for professional documentation.
Related Diagram Types
Class Diagram Maker
Design object-oriented structures with classes, interfaces, inheritance, and associations.
Flowchart Maker
Design process flows, decision trees, and workflows with our intuitive flowchart editor.
Sequence Diagram Maker
Visualize system interactions, API calls, and message flows between components.