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.
2-week trial, all features unlocked, no credit card. See all platforms
![The Schemity desktop app showing a PostgreSQL schema as an ERD: entities grouped into colored legends named auth, audit and account, crow's foot relationships between tables, red U badges for unique constraints, TEXT[] array columns on sso_configs, a minimap in the corner, and a status bar reading Entities: 59, Relations: 71, Context view: Main, PostgreSQL: 17.5](https://calendarstemplates.com/images/hero-erd@2x-1.webp)
PostgreSQL
Supabase
MySQL
MariaDB
SQL Server
SQLite
How Schemity Differs From Other ERD Tools
Most ERD tools are drawing canvases that live in a browser. Schemity is a desktop tool wired to the database it describes - and every difference below is one you can check in the first ten minutes of the trial.
It reads your database, and keeps up with it
Browser ERD tools take your schema as text you paste in, so the diagram starts drifting the moment the next migration lands. Schemity opens a real connection, reverse engineers the schema, and re-syncs every time you open the diagram: entities keep the layout you gave them, dropped tables disappear, and new ones arrive ready to place.
Many perspectives, one source of truth
Past about thirty tables, a single canvas stops being readable, and most tools answer with zoom and auto-layout. Schemity answers with Context Views - focused sub-diagrams you arrange freely while the schema itself stays untouched - and a Context Map that draws the dependencies between them from the real foreign keys.
The diagram is a file you own
In most tools the diagram is a row in the vendor's database, reachable for as long as you keep paying. Schemity writes plain JSON into a folder you choose, so a schema change is reviewed in a pull request as a diff - versioned, branched, and revertible with the tools you already use.
You can only draw what a database would accept
Most canvases let you join any column to any column and pick a cardinality from a menu. In Schemity a foreign key targets the parent's primary key, cardinality follows that key's uniqueness, referential actions are set per relationship, and duplicate table names are refused - so a diagram that looks valid is valid.
AI help that never routes through us
Cloud tools bundle AI as a metered feature and send your schema through their servers to get it. Schemity's assistant is bring-your-own-key: the schema goes straight to the provider you picked, on your account - or nowhere at all, if you point it at a local model through Ollama.
One purchase, and no meter on your model
Subscription tools price per seat and cap how many tables you may model, which quietly changes how you design. Schemity is $129 once, with no limit on tables, diagrams, workspaces, or Context Views - and no reason to merge two entities to stay under a quota.
Coming from a specific tool? Read the honest comparison: ChartDB, dbdiagram.io, DbSchema, DrawSQL, or Lucidchart.
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.
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.
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.
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.
Rapid Prototyping
Sketch your schema in seconds, before the idea fades.
Flexible Relationship Lines
Reshape any connector with custom waypoints and smart routing.
Check Constraints as Documentation
Fields with an IN constraint are underlined, with their allowed values one keystroke away.
Custom Entity Colors
Color an entity and every relationship leaving it inherits the color.
Clear Unique Together
Composite unique constraints render as named, color-coded badges.
Tabs as Systems
Open several diagrams at once, each with its own undo history.
Schemas as Structure
Model across PostgreSQL schemas, not just the public one.
AI Assistant
BYOK or local Ollama - your schema never routes through our servers.
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
Design your schema where it belongs - on your machine
$129 one time. Two-week trial with every feature unlocked, no credit card, and your diagrams stay yours whether you buy or not.
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.
