websequencediagrams is a great tool for people who want to generate UML sequence diagrams but who can't or don't want to layout their diagrams.

What it does is allow you to type the diagram specification (free typing) using a little markdown notation (I guess they made up) that's easy to learn. Whenever you change the block of text, the diagram changes. See picture.

enter image description here

This diagram was created from this text:

title Authentication Sequence

Alice->Bob: Authentication Request
note right of Bob: Bob thinks about it
Bob->Alice: Authentication Response


I want to create activity diagrams. But I'm getting a little impaired in my ability to use the mouse with precision. Also I know that if you change the structure of an activity diagram, then that can force radical changes to the layout of the diagram. Seems like a waste of time to be struggling with layout when all you wanted to do was just to represent something in UML.

Other requirements

I understand some people have different styles, but I don't care about the style in my case. It's a worthwhile trade-off.

I can either use windows or the web, but I'd prefer a web-based solution because that's portable.

I would be willing to pay for a tool that did this.

  • 1
    Did you have a look at plantuml (plantuml.com)?
    – albert
    Apr 7, 2019 at 16:21
  • @albert ok that's exactly what I was looking for. If you want to answer, I'll mark it. I see they reference in the running section a web-based implementation!
    – toddmo
    Apr 8, 2019 at 2:15

1 Answer 1


Plantuml is an UML drawing tool (based on an input file). From the website:

PlantUML is a component that allows to quickly write :

Sequence diagram
Usecase diagram
Class diagram
Activity diagram (here is the legacy syntax)
Component diagram
State diagram
Object diagram
Deployment diagram 
Timing diagram 

The following non-UML diagrams are also supported:

Wireframe graphical interface
Archimate diagram
Specification and Description Language (SDL)
Ditaa diagram
Gantt diagram 
MindMap diagram 
Work Breakdown Structure diagram 
Mathematic with AsciiMath or JLaTeXMath notation

See http://plantuml.com/

Furthermore there is a web based implementation: http://www.plantuml.com/plantuml/uml/SyfFKj2rKt3CoKnELR1Io4ZDoSa70000

and there is also a forum: http://forum.plantuml.net/questions


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