What is a sequence diagram?
A sequence diagram shows the order of messages between parts of a system over time, reading from top to bottom. This sequence-style template traces a login: the user clicks, the browser calls the API, the API checks the database, and replies flow back as dashed arrows. It is drawn with ordinary shapes, so you can adapt it freely.
When to use it
- Explaining an API flow, such as login, checkout or a webhook.
- Debugging a timing problem between services.
- Documenting an integration for another team.
How to make a sequence diagram in SketchFlow
- Step 1: Open the sequence diagram template in SketchFlow.
- Step 2: Rename the participant boxes at the top (and their matching boxes at the bottom).
- Step 3: Rewrite each message label; requests are solid arrows and replies are dashed.
- Step 4: Add a message by duplicating a pair of small activation boxes and drawing an arrow between them.
- Step 5: Export as SVG or PNG for your API docs.
Tips for a better result
- Time runs downward — never draw a message that goes back up.
- Use verbs for requests (POST /login) and nouns for replies (token).
- Show error paths on a separate diagram to keep this one readable.
Questions about this template
What is a sequence diagram?
It is a diagram, common in UML, that shows participants as vertical lifelines and the messages between them as horizontal arrows in time order.
Is this a strict UML sequence diagram?
It is sequence-style: it follows the same conventions with plain shapes. For formal UML features like combined fragments, use a dedicated UML tool.
Why are some arrows dashed?
By convention, solid arrows are requests or calls and dashed arrows are the replies.