As you can see in the GIF, ZenUML provides instant feedback to the user’s input. Websequencediagrams does not have the button, but it does a best-effort work to show the latest diagram. This is because they need to send the code to the backend server and get the picture back from the server. You have to click that button to get the resulting diagram. PlantUML and most other tools have a ‘Submit’ (or ‘Refresh’) button. If you insert the diagram into another document, it is indexable. Participant names, messages are all text on the page. This is already supported in the Chrome Extension. You can apply any styles on it – different colors, borders, fonts and even handwritten styles.While PlantUML produces diagrams as pictures (png, svg) and some other tools generate ASCII or draw on Canvas, ZenUML takes a different approach. So I had to find a better way for presenting nesting logic: ‘ IMHO, it quickly gets unreadable when you start nesting logic as you can see in the above video. One thing I am not quite happy with PlantUML is its DSL. I like the idea of generating diagrams from text because I hate to constantly drag-and-drop and double-click to edit names etc. Since then, I have tried quite a few tools, including PlantUML. I started using sequence diagrams heavily around 2006. The DSL to define sequence diagrams in ZenUML

System sequence diagram online tool