In which tool do you draw sequence diagrams? How to display multiple scenarios (success, errors, timeout) on one diagram using frames?

Tools like PlantUML, Visual Paradigm, Lucidchart, or draw.io are often used for drawing sequence diagrams. PlantUML is especially convenient because it allows describing diagrams with text and supports frames for grouping scenarios.

To display multiple scenarios (e.g., success, errors, timeout) on one diagram, frames with the keywords alt (alternatives) or opt (optional blocks) are used. Each frame corresponds to a separate scenario and is visually separated by a box with a label.

Example in PlantUML:

@startuml
actor User
participant System

User -> System: Request data
alt Successful response
    System -> User: Data
else Error
    System -> User: Error message
else Timeout
    System -> User: Timeout message
end
@enduml

This approach allows compactly showing all system behavior variants in one place.