Sequence diagram maker
Time runs down the page and participants run across it. Because order carries the meaning, messages are reordered by index rather than dragged — a sequence diagram whose steps are out of order is simply wrong.
No account. Saved in this browser until you export it.
The pieces
What goes on the canvas
- Actor
- A person outside the system
- Participant
- A system or component taking part
- Note
- A comment on a step
Building one
From blank canvas to finished diagram
- 1Add the participants left to right, roughly in the order they first get involved.
- 2Add messages between them, top to bottom, matching the order they actually happen in.
- 3Mark returns where the reply matters. Where it does not, leaving it out keeps the diagram readable.
- 4Messages are drawn top to bottom in the order you add them, with a dashed lifeline under each participant. Select a message and use Earlier or Later to change its place in time.
Examples
Start from a real one
Where it helps
Good uses
Explaining an integration
What calls what, in what order, and what comes back.
Debugging a race
Drawing the interleaving often finds it.
API design review
Round trips are obvious once they are drawn.
Incident write-ups
The timeline of a failure, as a picture.
Questions
Asked often
- Is message position automatically time-ordered?
- Yes. Each message sits at the height given by its place in the order, and lifelines extend below the participants to the last message. You arrange the participants left to right yourself; to move a message in time, select it and press Earlier or Later. Each move is one undo step.
- Can I show return messages?
- Yes. Select a message and mark it as a Reply: it is drawn dashed with an open arrowhead. Calls are solid with a filled arrowhead.
- Does DiagramDock itself use an API?
- No. But diagrams can obviously describe systems that do.
Draw the conversation
Nothing to sign up for. The diagram stays on this device.