The Offline ERD Tool
Built For Software Engineers
Schemity is an offline desktop ERD tool for software engineers on macOS, Windows, and Linux - a $129 one-time purchase, no cloud, no subscription. Break complex schemas into focused Context Views - one source of truth, many perspectives - stored as Git-friendly JSON files that never leave your machine.
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Visual Modeling That Stays Out of Your Way
A schema visualizer with smart defaults, drag-and-drop relationships, and a visual editor that gets out of your way - so your team spends time understanding the schema, not fighting the tool.
Rapid Prototyping
Sketch your schema in seconds. Go from concept to concrete entities before the idea fades.
Smart Relationships
Create 1:N, 1:1, or N:N relationships with simple drag-and-drop. Auto junction table generation, auto FK naming - no manual wiring needed.
Flexible Relationship Lines
Arrange your ERD the way you think about it, not the way the layout forces you. Lines adapt and reroute automatically, turn with rounded corners, and hop over each other where they cross. Add ERD custom waypoints for full control.
Check Constraints as Documentation
Full check constraint support - write any expression you need. For IN constraints, Schemity extracts the allowed values into a selectable dropdown for default values - self-documenting and enforceable in one step.
Custom Entity Colors
Group related entities visually. Color-code entity groups and their relationship lines for instant clarity on large schemas.
Clear Unique Together
Instantly distinguish between single-field unique constraints and ERD composite unique constraints at a glance.
Safe Migration Workflow
Every schema change requires explicit migration confirmation - no accidental alterations to your database. Review the exact ERD migration SQL diff before applying.
Tabs as Systems
Use tabs to separate the systems you work on - one product, one tab. Quick number-key navigation keeps you focused as you move between domains.
Schemas as Structure
Model across PostgreSQL schemas - not just the public schema. Use them to express domains and structural boundaries inside a single database.
Import SQL/DBML
Import CREATE TABLE statements, a SQL dump file, or a DBML file. Schemity builds entities, fields, and relationships automatically - no database connection needed. Export back to DBML anytime.
AI Assistant
AI ERD without cloud - full control from chat. Create entities, define relationships, edit or delete fields, and import entities into Context Views. BYOK - your data goes directly to your AI provider, never through our servers. Or chat with local models via Ollama and keep everything on your machine.
How Schemity Works: Three Steps From Database to Documented Schema
Connect your database, break it into focused Context Views, and evolve the schema with confidence - all from a single source of truth.
Connect, Import, or Start Fresh
Reverse engineer PostgreSQL to ERD in seconds, visualize a MySQL schema on your desktop, or start from scratch. Get a complete visual picture of your schema - no weeks of manual documentation. Everything stays on your machine.
Break It Into Context Views
Reduce 50 tables down to a 10-table focused view. Create one Context View per concern - auth, billing, analytics - ready for audits, handovers, or onboarding new team members.
Evolve with Confidence
Schemity diffs your ERD against the live database and generates the exact SQL migration. Your ERD lives as plain JSON in your repo - no third-party server ever sees your schema.
See How Your Bounded Contexts Depend On Each Other
Context Views zoom you in on one part of the schema. The Context Map zooms you out: every context becomes a single node, and the arrows between them are derived from the foreign keys that actually exist in your database - so the map cannot drift from the schema.
- Every arrow is counted. A badge shows how many foreign keys flow that way, so coupling between contexts is a number, not a feeling.
- Circular dependencies show up as curves. A straight arrow is one-way; a curved one means both contexts depend on each other.
- Double-click for the actual foreign keys. Source field, target entity, constraint name - a suspicious arrow becomes a list of columns to fix.
- Ask the AI about your architecture. The BYOK assistant finds indirect cycles spanning several contexts, which no visual scan can reveal.
Read the Context Map documentation or the deep dive on deriving a DDD context map from your foreign keys.
Why Schemity Has No Real-Time Co-Editing
Schema design is deep work: one designer holds the pen, and the whole room debates the design.
For me, ERD design is a serious task that consumes real mental energy. While I am designing, the whole model lives in my head - every name, every boundary, every relationship I am about to draw. If someone renames a field or drags an entity somewhere else in the middle of that, it is not a merge conflict. It is a disaster.
Collaboration on a schema should work the way it does in a real design room or an online meeting: the person in charge of the design sits at the keyboard, the diagram goes up on a projector or a screen share, and everyone discusses, challenges, and proposes. Then one pair of hands applies the outcome. The discussion is collective. The canvas is not.
So Schemity has no real-time co-editing - by design, not by omission. Feedback happens the way engineers already review everything else: the ERD lives as plain JSON in Git, so a proposed change arrives as a diff and comes back as review comments - never as a surprise edit to the diagram you are working on.
- Son Tran, creator of Schemity
Security: Your Schema Never Leaves Your Machine
An ERD tool with no cloud means your client's schema never touches a third-party server. What we don't store, we don't have to protect - and you don't have to audit. Safe for NDA projects, client work, and air-gapped environments.
No Personal Data Stored
We only store an auto-generated device ID and your country - for license management and regional support. No name, no email, no usage tracking. Nothing that identifies you.
Payments Handled by LemonSqueezy
All payment processing and billing are managed by LemonSqueezy. Schemity never sees or stores your payment information.
SOC 2 and ISO 27001 Ready
Because Schemity stores almost nothing, it largely satisfies SOC 2 and ISO 27001 requirements by design. Your ERD files live locally in your repo - not on our servers.
Native on Every Platform
Experience seamless performance and native feel across all major operating systems.
macOS
Windows
Linux
Browser
Notes on Schema Design and ERD Perspectives
Working notes on context views, ERD best practices for software engineers, and the principles behind a Git-native ERD tool. The latest few posts.