Schemity

Schemity is an offline desktop ERD (Entity Relationship Diagram) tool for software engineers and database designers. It runs fully offline - no cloud, no account required - and stores every diagram as a plain local JSON file, so your schema design can live in the Git repository next to the code it describes. No limits on workspaces, diagrams, or tables.

Database Integration

• Connect to PostgreSQL, Supabase, MySQL, MariaDB, SQL Server, and SQLite, directly or through an SSH tunnel
• Reverse-engineer an existing database into a diagram, with foreign keys, constraints, and referential actions intact
• Re-sync on reopen pulls the live schema while existing entities keep their layout; new tables arrive ready to place, dropped ones disappear
• Diagram edits generate a migration SQL diff you review first - nothing runs against the database until you approve it
• Passwords stored in the OS keychain; SSH connections store only a reference to your private key
• Import SQL (CREATE TABLE statements or a full dump) or DBML; pure design mode needs no connection at all

Visual Design

• Entities, fields, indexes, check constraints, and named composite unique constraints
• 1:1, 1:N, N:N, and self-referencing relationships; N:N automatically creates the junction table with both foreign keys and a composite primary key
• Cardinality is derived from the foreign key's uniqueness rather than drawn by hand, and ON DELETE / ON UPDATE are configurable per relationship
• Views and materialized views render as read-only entities; PostgreSQL array types and check-constrained enum-like fields are shown as what they are
• Entity colors that relationship lines inherit, line hops where lines cross, custom waypoints, snap guides, and legends

Context Views and the Context Map

• A context view is a focused subset of the main diagram - a sub-diagram you arrange freely while the schema itself stays untouched, so the main view remains the single source of truth
• The Context Map renders each context view as a node and draws the dependencies between them, counting the foreign keys behind every arrow

AI, on Your Own Terms

• Bring your own key for OpenAI, Claude, Gemini, Grok, or DeepSeek, or run entirely locally through Ollama with no cloud at all
• The assistant edits the diagram directly: it creates and modifies entities and relationships, arranges the Context Map, and finds circular dependencies between contexts

Productivity

• Keyboard-first with vim-style navigation (h/j/k/l), full undo/redo, multi-tab editing, and copy/paste across diagrams
• Entity templates and realtime fuzzy search across both entity and field names

Export and Portability

• PNG, JPEG, and true-vector SVG that opens as editable artwork in Affinity Designer, Illustrator, and Inkscape
• SQL DDL for the whole diagram, a context view, a legend, or one entity
• DBML in and out, plus Mermaid erDiagram export that GitHub, GitLab, Notion, and Obsidian render natively

Available on macOS, Windows, and Linux.