UML Diagram Generator

How to use this UML diagram generator

This tool is designed for fast, lightweight UML diagrams. Instead of dragging shapes around, you describe your model in text and the generator lays it out automatically.

1. Choose a diagram type

Use the Diagram type dropdown to switch between:

• Class diagram – classes, attributes, methods, and relationships.
• Sequence diagram – participants and messages over time.
• Use case diagram – actors and use cases.
• State diagram – states and transitions.

2. Describe your diagram in text

Paste or type your description in the editor. The syntax is intentionally simple and inspired by PlantUML and yUML, but more forgiving.

Class diagram syntax

# Classes
class User {
  +id: int
  +name: string
  +login()
}

class Order {
  +id: int
  +total: decimal
}

# Relationships
User -> Order : places
Order --> User : belongs to
User --|> Admin

• class Name { ... } defines a class.
• Inside braces, each line is an attribute or method.
• Use ClassA -> ClassB : label for associations, --|> for inheritance.

Sequence diagram syntax

# Participants
participant User
participant API
participant DB

# Messages
User -> API : login(email, password)
API -> DB : query user
DB --> API : user found
API --> User : login success

Use case diagram syntax

actor Customer
actor Admin

usecase "Place Order"
usecase "Manage Products"

Customer -> "Place Order"
Admin -> "Manage Products"

State diagram syntax

state Idle
state Loading
state Error
state Success

Idle -> Loading : fetch()
Loading -> Success : ok
Loading -> Error : fail
Error -> Idle : retry()

3. Render, adjust, and export

1. Click Render diagram to update the preview.
2. Use the Layout dropdown and zoom controls to adjust the view.
3. Export as PNG or SVG for documentation, wikis, or slide decks.

Why use a text-based UML generator?

Compared with heavy visual tools like draw.io, Lucidchart, or SmartDraw, a text-based UML generator is:

• Faster for iteration – edit a few lines instead of dragging dozens of boxes.
• Version-control friendly – store the source text in Git alongside your code.
• Consistent – automatic layout avoids misaligned shapes and overlapping arrows.
• Lightweight – runs entirely in the browser, no login or account required.

Tips for clean UML diagrams

• Keep names short and meaningful – e.g. OrderService instead of ServiceForHandlingOrders.
• Group related elements together in the text; the layout engine will usually place them near each other.
• Limit relationships – too many arrows can make diagrams hard to read. Focus on the most important ones.
• Use multiple diagrams – one class diagram per bounded context is often clearer than a single huge diagram.

Frequently asked questions

Does this support full PlantUML syntax?

No. This generator intentionally supports a subset of PlantUML-like syntax that covers the most common UML needs (classes, relationships, participants, messages, states). If a line is not recognized, it will be ignored or flagged in the error panel.

Can I use this for professional documentation?

Yes. The output SVG and PNG files are suitable for architecture docs, ADRs, wikis, and slide decks. For very large enterprise diagrams you may still prefer a dedicated modeling tool, but for most day‑to‑day diagrams this generator is more than enough.

Is there a limit on diagram size?

There is no hard limit, but very large diagrams with hundreds of nodes may become slow to render in the browser. In that case, consider splitting the model into several smaller diagrams.