Mermaid to ER Diagram

How it works

1. Copy your Mermaid erDiagram block.
2. Paste it into the editor — Mermaid is auto-detected.
3. Each entity becomes a table; relationships are drawn with the right cardinality.
4. Arrange, hide tables, then export PNG/SVG or convert to DBML/PlantUML.

Example

A Mermaid erDiagram like this:

erDiagram
  USERS ||--o{ POSTS : writes
  USERS {
    int id PK
    string email
  }
  POSTS {
    int id PK
    int user_id FK
  }

…renders two tables with a relation between USERS and POSTS. Try it with your own →

Guide

Mermaid erDiagram blocks are everywhere — GitHub READMEs, GitLab wikis, Notion pages, Obsidian notes — but the default renderer gives you a static picture you can't touch. Paste the same block here and you get a live canvas: every entity becomes a draggable table, every relationship keeps its crow's-foot cardinality, and you can export the result as an image or convert it to DBML or PlantUML.

Cardinality notation reference

• ||--o{ — exactly one to zero-or-many (the classic parent-child).
• ||--|| — one to exactly one.
• }o--o{ — zero-or-more to zero-or-more (many-to-many).
• Attribute keys: PK, FK, and UK markers on attribute lines are rendered as key badges.

Entities defined only by relationship lines (no attribute block) render as compact nodes — useful when your diagram is at the "sketch" stage. Comments in double quotes after the relationship (: "places") are kept as edge labels.

Why use it

• Private: everything runs in your browser — nothing is uploaded or stored on a server.
• Interactive, unlike a static Mermaid render — drag, arrange and hide tables.
• Export a high-res PNG, vector SVG, or the schema as Mermaid / DBML / PlantUML code.
• Free & open source — no account, no sign-up.

FAQ

Can I edit a Mermaid ER diagram visually?

Paste the Mermaid erDiagram to render it, then drag and arrange tables on the canvas. You can also convert it to SQL-style images or DBML via Export.

Does it support Mermaid cardinality?

Yes — one-to-one, one-to-many and many-to-many crow’s-foot notations are recognised and drawn.

Is my schema uploaded anywhere?

No. Everything runs locally in your browser — your schema is never uploaded to or stored on any server.

Is it free?

Yes. It is completely free and open source, with no account or sign-up required.

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