erdalchemy is an interactive ERD visualizer for SQLAlchemy 2.0 models. Point it at your DeclarativeBase and get a diagram, no manual configuration.

• Drag-and-drop interactive HTML, with hover highlighting
• Three layouts: hierarchical layered (default), force-directed, and star
• Orthogonal edge routing that follows foreign keys without cutting across cards
• Regex filtering to focus large schemas (include/exclude tables and columns)
• Export to HTML, SVG, PNG, and PDF
• Built-in themes and per-table color overrides
• Multi-schema support with cross-schema FKs
• Zero dependencies beyond SQLAlchemy

Install

pip install erdalchemy

PNG and PDF export need an optional dependency:

pip install "erdalchemy[all]"

Quick start

from sqlalchemy_erd import generate_erd
from myapp.models import Base

generate_erd(Base, output="erd.html")

Or from the command line:

sqlalchemy-erd myapp.models:Base --format svg --output erd.svg

Layouts

Layout	When to use
layered (default)	General purpose. Ranks tables into columns by FK direction; cards never overlap. Best for large or wide schemas.
force	Small, highly-connected graphs where an organic shape reads better.
star	Star/snowflake and ETL schemas, or many disconnected tables.

generate_erd(Base, output="erd.html", layout="layered")

Documentation

Full reference (every CLI flag, the Python API, themes, layout tuning, card sizing, and supported column types) lives in docs/reference.md.

Examples

See examples/ for ready-to-run schemas:

• showcase/ - 12 tables across four FK levels (the preview above)
• blog/ - blog schema (User, Post, Comment)
• ecommerce/ - 1:N chains
• university/ - N:N via association tables
• hr/ - 1:1 and 1:N
• multi_schema/ - cross-schema FKs

Acknowledgments

Inspired by eralchemy2 (originally eralchemy), which pioneered generating ER diagrams from SQLAlchemy models. erdalchemy reimagines the idea with a self-contained, interactive, dependency-free renderer.

License

MIT