Sequence Diagram Generator
Write one message per line with A -> B: message or A --> B: reply. The tool discovers participants in first-seen order and draws lifelines, arrows, and labels.
One line per message: sender -> receiver: label or sender --> receiver: reply. Up to 200 messages and 50 participants.
Download SVGA QUICK WALKTHROUGH
How to use this tool
- Enter up to 200 message lines using the supported arrow syntax.
- Generate and inspect the diagram; correct any line called out as invalid.
- Download the generated SVG for documentation or further editing.
Small explicit syntax
Each nonblank line must be sender -> receiver: message or sender --> receiver: message. Participant names and messages are plain text; activation blocks, notes, loops, and UML execution semantics are outside this version.
Bounded local rendering
Input stays on this page and is limited to 100,000 characters, 200 messages, 50 participants, 80 characters per participant, and 200 characters per message.
SVG output
The generated SVG uses escaped text, fixed geometry, and no external resources. Long diagrams can be tall; labels are shortened visually when needed while the input remains unchanged.
GOOD TO KNOW
Common questions
Does this understand Mermaid or PlantUML?
No. It accepts only the two arrow forms documented on this page.
Is my diagram uploaded?
No. Parsing and SVG generation happen in the browser.
Can I edit the SVG later?
Yes. Download it and open it in an SVG-aware editor.