Login Sequence Diagram

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Mermaid

Map every step of user authentication. This template shows the back-and-forth between a user, your login interface, validation logic, and database — making it clear where credentials are checked, how responses flow back, and what happens after successful authentication. It's a straightforward way to document login flows, debug authentication issues, or explain security processes to your team without getting lost in technical specs.

How to create a Login Sequence Diagram

To create a login sequence diagram, follow these steps:

01.
Identify actors
Define who or what participates in the login process (e.g., user, login page, authentication service, database).
02.
Determine system boundaries
Clearly specify what's inside your authentication flow and what external systems are involved (e.g., third-party auth providers, session managers).
03.
List interactions
Identify the main messages exchanged between actors (e.g., "click login," "validate credentials," "return user data").
04.
Create lifelines
Draw vertical dashed lines representing each actor and system component throughout the sequence.
05.
Add messages
Use arrows to represent the flow of requests and responses between lifelines, labeling them with specific actions.
06.
Order events
Place messages in chronological sequence from top to bottom, showing the exact order of authentication steps. Add branches (optional): Wrong password, locked account, MFA required, rate-limit, password reset.
07.
Review & share
Walk through with your team to confirm the happy path and edge cases.

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Tags

SecurityAuthenticationSequence DiagramLogin FlowBackendOnboardingError Handling

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