Schemity

Schemity is database design software for software engineers. It reads your live database into an ERD, gives your AI agent a local MCP server, and shows the impact of every schema migration before it runs. Everything stays on your machine: no cloud, no account, and every diagram is a plain JSON file you commit to Git. One-time purchase, no limits on diagrams or tables.

Understand Your Schema

• Connect to PostgreSQL, Supabase, MySQL, MariaDB, SQL Server, and SQLite, directly or through an SSH tunnel
• Read an existing database into a diagram with foreign keys, constraints, views, and referential actions intact
• Re-sync on reopen pulls the live schema while every entity keeps its place
• Context views split a large schema into focused sub-diagrams; the Context Map draws the dependencies between them
• Export a data dictionary as HTML, Markdown, or Excel

See the Impact of Every Change

• Impact analysis shows what a pending migration costs: lost data, statements that fail on existing rows, table rewrites, locks on large tables, and dependent views, triggers, and functions
• Analyze a migration file from Prisma, Alembic, Flyway, an AI agent, or your own hand against the connected database without executing it
• Preview changes draws dropped, added, and altered tables and columns
• Schema lint marks design problems on the exact entity and field row, such as an unindexed foreign key or a unique constraint over a nullable column
• Every edit becomes a migration SQL diff you review first; production connections can require typing the database name before applying

Your AI Agent, on a Governed Path

• A local database MCP server for Claude Code, Claude Desktop, Cursor, Codex, and OpenCode
• Your agent reads the schema, dependencies, and the cost of pending changes; its edits are staged for you to review and undo
• No vendor cloud in the middle: your schema goes only where your agent already sends your code

Design the Next One

• Entities, fields, indexes, check constraints, and composite unique constraints
• 1:1, 1:N, N:N, and self-referencing relationships; N:N creates the junction table for you
• Cardinality follows the foreign key's uniqueness; ON DELETE / ON UPDATE set per relationship
• Import SQL or DBML, or design with no database connection at all
• Templates, legends, custom waypoints, line hops, and smart snapping

Fast and Private

• Keyboard-first with Vim-style navigation, tabs, full undo/redo, and fuzzy search
• Passwords in the OS keychain or from a shell command (RDS IAM tokens, Vault, a password manager)
• Interface in English, Japanese, and Simplified Chinese

Export

• PNG, JPEG, and true-vector SVG editable in Figma, Illustrator, and Inkscape
• SQL DDL, DBML, and Mermaid erDiagram for GitHub, GitLab, Notion, and Obsidian

macOS, Windows, and Linux, with a 2-week free trial. Schemity Lite, the free browser version, lets you design and share diagrams with no install.