ERD Chart

Free Online ERD Chart Maker

What is an ERD Chart?

An Entity Relationship Diagram (ERD) is a visual blueprint of a relational database, showing tables as entities, columns as attributes, and lines as the relationships between them. ERDs are essential for database design, helping teams align on schema structure before writing a single line of SQL. Use one when planning a new application, documenting an existing database, or communicating how your data fits together across a system.

Key Features

Entity Blocks with Attributes

Define each database table as an entity with named attributes, data types, and optional comments — exactly like a schema spec.

PK, FK, and UK Annotations

Mark primary keys, foreign keys, and unique keys directly on attributes so relationships and constraints are immediately clear.

Cardinality Notation

Set source and target cardinality per relationship — exactly one, zero or one, one or more, zero or more — using standard crow's foot symbols.

Identifying vs Non-Identifying Relationships

Distinguish whether a child entity depends on the parent for its identity, a critical distinction for correct normalization.

Flexible Layout Directions

Arrange entities top-to-bottom, left-to-right, or any orientation to fit the natural flow of your schema.

Zoom and Pan Navigation

Explore large, complex diagrams with smooth zoom and pan so no entity gets lost off-screen.

Best For

Designing relational database schemas before development

Documenting an existing database for a new team member

Planning foreign key constraints and join paths

Backend architecture reviews and technical specs

Data modeling for SaaS, e-commerce, or internal tools

Teaching relational database concepts with a live visual

When to Use

You are designing a new database and need to map out tables and relationships before writing SQL
You need to communicate schema structure to developers, analysts, or stakeholders
You are auditing or refactoring a legacy database and want a clear picture first
You need to identify missing foreign keys or redundant tables
You are onboarding someone to an existing system and want a single reference diagram
You are writing technical documentation that must include a data model

Common Mistakes

Skipping foreign key annotations — relationship lines alone do not show which attribute carries the FK
Cramming every column into one diagram instead of focusing on the key attributes that define relationships
Leaving relationship lines unlabeled, so viewers cannot tell what the association means
Mixing cardinality styles mid-diagram (Chen notation circles vs. crow's foot) — pick one and stick to it
Not distinguishing identifying from non-identifying relationships, which changes how child records are keyed
Drawing many-to-many relationships directly instead of introducing the junction table that implements them

Related Tools

Create similar charts with these tools

AI ERD Diagram Generatorerd

Build accurate ER diagrams fast with our AI entity relationship diagram generator. Free, online, customizable, and export-ready (PNG/SVG). Create, edit, and share ERDs in minutes—no design skills needed.

AI ERD Makererd

Create accurate schemas fast with our ERD maker for database design. Auto-build entities and relationships, customize layout and labels, then export or share—free online.

ERD for Postgres & MySQLerd

Design clear ER diagrams for PostgreSQL and MySQL online. AI maps PK/FK, cardinality, and layout. Free to start, customize, and export or embed in seconds.

AI ERD Diagram Generatorerd

Design clean ER diagrams fast. Our database schema diagram tool uses AI to map entities, PK/FK keys, and cardinality. Free to start, customize layout, and export.

Templates

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