NodlumeER diagram designer
Model your database visually — no account needed. Add entities with typed columns, draw 1–1, 1–N and N–N relations (many-to-many creates the join table a relational model actually needs), and export a Mermaid erDiagram that renders on GitHub, in docs sites and in most editors. Your diagram is saved in this browser as you draw.
Draw relations, get keys
Drag a relation between two entities and the foreign key appears on the right side with the right type — unique for 1–1, a join entity with both keys for N–N. The diagram and the columns can never disagree.
Schema-agnostic on purpose
Mermaid out, not a migration: the same diagram can be written into Postgres, Prisma, Drizzle or Mongo. A picture of the model is the part every stack shares.
Readable anywhere
GitHub renders .mmd natively, so the export drops straight into a repo's docs — typed columns, PK/FK/UK markers and crow's-foot cardinality included.
ER diagrams, answered
- Does it generate SQL or a migration?
- No, and that is deliberate. The export is a Mermaid erDiagram — a picture of the model rather than DDL for one database. The same diagram can then be written into Postgres, MySQL, Prisma, Drizzle or Mongo, which is why the board stays schema-agnostic instead of committing you to an engine while you are still deciding what the entities are.
- How are many-to-many relationships handled?
- Drawing an N–N relation creates the join entity a relational model actually needs, carrying a foreign key to each side. One-to-one and one-to-many add the foreign key directly, unique for 1–1. The columns are derived from the relations you draw, so the diagram and the keys can never disagree with each other.
- Is my diagram saved, and do I need an account?
- No account is needed and nothing is uploaded. The diagram is saved in your own browser as you draw, so it is there when you come back on the same browser — and it is not there on a different device, so export the Mermaid when you want to keep or share it. Signing up moves the same board into a Nodlume project, where it syncs and can be collaborated on.
Model the data next to the app it serves
In the Nodlume workspace this board is one tab of a full product designer — the entities you draw here ground the generated types, API routes and test cases of a real Next.js project, with AI generation and real-time collaboration on top.