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Mermaid to ER Diagram

Paste a Mermaid erDiagram and turn it into a fully interactive ER diagram you can drag, auto-arrange, and export — no Markdown renderer required.

Open the diagram tool →

No signup · nothing uploaded · export PNG / SVG / Mermaid / DBML · shareable link

ER diagram of the Mermaid example schema: USERS and POSTS (2 tables, 2 relationships) — The Mermaid example below, drawn by the tool: USERS and POSTS (2 tables, 2 relationships).

At a glance

What it is: SQL to ER Diagram is a free, open-source browser tool that turns a Mermaid erDiagram into an interactive entity-relationship (ER) diagram.
Input: A Mermaid erDiagram block.
Output: An interactive ER diagram you can rearrange, then export as PNG, SVG, Mermaid, DBML or PlantUML, or share as a link.
Cost: Free. MIT-licensed open source. No account or signup.
Privacy: Runs entirely in your browser. The schema is never uploaded, and share links carry the diagram in the URL fragment, which is not sent to a server.
Limits: It never connects to your database itself: you paste schema text, or run one read-only catalog query in your own client and paste the result. There are no accounts, so there is no real-time multi-user editing; diagrams are kept in your browser, as a saved file, or as a share link. Layout stays smooth at around 300 tables.

How it works

Copy your Mermaid erDiagram block.
Paste it into the editor — Mermaid is auto-detected.
Each entity becomes a table; relationships are drawn with the right cardinality.
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.

MermaidDBMLPlantUMLSQLPrisma

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.