What is ERD Online
If you want something that remembers schema changes like Git and edits like a canvas, you are in the right place.
In one line: open-source (MIT) database modeling — versions, diffs, self-hosting; or try the free Demo first.
A good fit if you…
- Need a design-time trail of who changed which fields, and when
- Want to move from dbdiagram / a live DB into a collaborative, self-hostable tool
- Want open
projectJSON/ API / MCP so scripts or agents share one source of truth
Probably not if you…
- Only need a static ER screenshot → draw.io or another drawing tool may be lighter
- Only care about applied DDL history → keep Flyway (etc.); we cover design-time tracing
- Need full enterprise IAM / SSO out of the box → we offer project-level roles & approval, not a full IAM suite
Capabilities you will use often
| Capability | You get |
|---|---|
| Relationship canvas | Visual edit of tables, columns, FKs |
| Versions & diffs | Snapshots; compare tables / columns / relations |
| DBML import/export | Interop with tools like dbdiagram |
| Reverse engineering | MySQL / PostgreSQL / Oracle / SQL Server |
| Collaboration & access | Shared projects; roles & SQL approval |
| Self-host | docker compose up -d |
| Agent / MCP (secondary) | Cursor prompt suggest-erd-version: same projectJSON, then create_version for a human diff. The public Demo is not a PAT |
What you see on first Demo open
- An example project (e.g. RBAC / business tables) with tables and relations
- The top bar may say Read-only: this is a shared demo, not an empty landing shell
- To edit and save versions: click Copy to my project (or Sign in / Register first)
If the page spins forever or stays blank, see troubleshooting below.
FAQ
| Symptom | Try |
|---|---|
| Demo won’t open / endless spinner | Retry network; confirm www.erdonline.com/demo |
| Want to edit but see read-only | Copy to my project or sign in, then open the designer |
| Want to connect your own DB | Public demo/share cannot reach private DBs → Quick self-host |
| Want to compare with draw.io / dbdiagram | Compare page (includes an FK-semantics row and Agent/MCP) |
| Want Cursor to read the diagram you are editing | The public Demo is not a PAT. Copy to your own project, mint a token, then follow the MCP guide; pick prompt suggest-erd-version. create_version API 200 is not human approval |
Next steps
- Save a version and view the diff — core loop (recommended)
- Import DBML or Reverse engineer
- Quick self-host
- Let Cursor read your ER diagram via MCP — secondary; pick prompt
suggest-erd-version; API 200 is not human approval
Maintainer positioning essay: Vision