This is a free online tool to create sequence diagrams where all processing of parsing and painting the diagram is done using javascript client side in the users web browser. This not only makes it snappy to work with, but it also means that secrets are safe if you chose to put any into the diagram. Since no backend server is used it is also possible to use the web application offline. This makes it nicer to work with compared to the other alternatives out there.

This is also the only sequence diagram tools which allows you to:
* Script using a simple text notation when it is most convenient to do so, and
* Interact using you mouse to draw arrows or create notes when that is most convenient.

In other words bringing the best from both worlds. This makes it very easy to work with large diagram where other similar tools struggle. It also doesn't have any ads or other clutter. (Even the top bar can be hidden to maximize the working area)

The tool supports the main functionalities of UML sequence diagrams. The source code of the diagrams can be save as text files directly to your hard drive. There are also single click button to save the diagram in HQ png or LQ jpeg format.

If you want to share a diagram with others there is a URL share button available. It creates a link containing all the data of the diagram and can be sent to others so that they can view your diagram.

The tool is developed and maintained by people who create a lot of sequence diagrams and simply wasn't 100% satisfied with the existing offering, normally they were too slow, contained ads or just not very efficient to work with. This tool aims to solve all the above issues and be a time saver in our daily work.