How do I create a UML class diagram?

Start by listing your classes along with their attributes and methods, then identify the relationships between them: inheritance, composition, aggregation, or plain association. Each class renders as a rectangle split into three compartments for the name, attributes, and methods respectively. Solid arrows with hollow triangleheads indicate inheritance; filled diamonds mark composition; hollow diamonds mark aggregation. With Figviz you can skip the manual drawing entirely and let the AI produce a correctly notated class diagram from a short description.

What is the difference between a use case diagram and a sequence diagram?

A use case diagram answers the question of what the system offers, showing high-level capabilities as ovals and mapping them to the actors who trigger them. A sequence diagram answers the question of how a capability works, ordering the messages between objects on a timeline to fulfill one specific use case. Use case diagrams fit requirements workshops, while sequence diagrams fit detailed design sessions where the exact order of operations matters.

When should I use a sequence diagram vs an activity diagram?

Reach for a sequence diagram when the critical information is which objects talk to which and in what order, such as for API call chains, login flows, or distributed protocol exchanges. Reach for an activity diagram when the critical information is what steps happen and how control branches or joins, such as for order processing pipelines, document approval workflows, or batch data jobs. Sequence diagrams centre on participants and their messages; activity diagrams centre on steps, decisions, and parallel paths.

Can UML diagrams be used for software architecture documentation?

UML is one of the most widely adopted standards for software architecture documentation. Component diagrams expose system modules and their interfaces, deployment diagrams bind software artifacts to the hardware or cloud resources they run on, and package diagrams organize code into logical groupings. Used together, these views give new team members and auditors a structured way to understand, maintain, and extend a complex system. Enterprise frameworks such as TOGAF and Zachman treat UML as a core modeling notation.

What UML notation symbols should I know?

The most common UML symbols are: rectangles for classes and objects, ovals for use cases, stick figures for actors, solid lines for associations, dashed lines for dependencies, hollow triangleheads for inheritance, filled diamonds for composition, hollow diamonds for aggregation, rounded rectangles for states, diamond shapes for decisions, and horizontal bars for fork and join nodes in activity diagrams. Figviz applies all of these symbols correctly by default, so any software professional can read your output without needing a separate reference.

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UML Diagram Generator UML Diagrams

Describe your system and Figviz will produce a standards-compliant UML diagram with correct notation. Works for class diagrams, sequence diagrams, use case diagrams, activity diagrams, and more.

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UML Diagram Examples

Browse software engineering examples or generate your own above

Class Diagram - Object-Oriented Design

An object-oriented class diagram that maps out an Animal hierarchy, with Dog, Cat, and Bird extending the base class. Each box lists attributes and methods across three compartments, with arrows indicating inheritance, composition, and aggregation.

class-diagramoopinheritance

Use Case Diagram - E-Commerce System

A use case diagram scoping an e-commerce platform. Customer and Admin actors connect to ovals representing Browse Products, Add to Cart, Checkout, and Manage Inventory, with include and extend relationships drawn between related cases.

use-caseecommercesystem-design

Sequence Diagram - API Interaction

A sequence diagram tracing an API call from the Client through an API Gateway, an Authentication Service, and a Database. Activation bars mark when each component is active, and return messages show the data flow back to the caller.

sequence-diagramapiclient-server

Activity Diagram - Document Approval Workflow

A swimlane activity diagram separating Author and Reviewer responsibilities. Decision diamonds route documents through approval or revision paths, while parallel fork and join bars capture concurrent review steps before reaching the final node.

activity-diagramworkflowapproval

State Machine Diagram - Order Processing

A state machine tracking an order through New, Confirmed, Processing, Shipped, Delivered, Cancelled, and Returned. Guard conditions on each transition specify the exact events that trigger a state change, making the lifecycle explicit and unambiguous.

state-machineorderprocessing

Component Diagram - Microservices Architecture

A component diagram laying out a microservices system. Frontend communicates through an API Gateway that routes to User, Product, Order, and Payment services. Lollipop notation marks provided and required interfaces, and dependency arrows show inter-service relationships.

component-diagrammicroservicesarchitecture

Prompt templates you can copy

Start with one of these examples, then adapt the subject, labels, data, or layout for your own use.

Class Diagram - Object-Oriented Design

Create a professional UML class diagram showing object-oriented design with classes Animal, Dog, Cat, Bird inheriting from Animal, with attributes and methods listed in compartments, showing inheritance arrows, composition and aggregation relationships, standard UML notation, clean software engineering style, white background

Use Case Diagram - E-Commerce System

Create a UML use case diagram for an e-commerce system with actors Customer and Admin, use cases including Browse Products, Add to Cart, Checkout, Process Payment, Manage Inventory, View Reports, showing include and extend relationships, standard UML oval notation with system boundary, professional style, white background

Sequence Diagram - API Interaction

Create a UML sequence diagram showing client-server API interaction, lifelines for Client, API Gateway, Authentication Service, Database, with synchronous messages for login request, token validation, data query and response, activation bars and return messages, standard UML notation, professional software design style, white background

Activity Diagram - Document Approval Workflow

Create a UML activity diagram for a document approval workflow, with initial node, decision diamonds for review stages, parallel fork and join bars for concurrent reviews, action nodes for Submit, Review, Approve, Reject, Revise, final node, swimlanes for Author and Reviewer roles, standard UML notation, white background

What Are UML Diagrams?

UML, short for Unified Modeling Language, is a standardized visual language that software teams use to model the structure and behavior of systems. Created in the 1990s by Grady Booch, James Rumbaugh, and Ivar Jacobson, it became the accepted industry standard for design documentation. A well-drawn UML diagram helps engineers share complex architectural ideas, nail down requirements, and map out an implementation plan before a single line of code is written. By bridging abstract concepts and concrete designs, UML keeps both agile sprints and traditional project plans on the same page.

14 Types of UML Diagrams Explained

UML covers 14 diagram types split into two broad families. Structure diagrams capture static relationships: Class Diagrams lay out classes and their connections, Object Diagrams freeze a snapshot of instances at runtime, Package Diagrams group namespaces logically, Component Diagrams map modules and their interfaces, Composite Structure Diagrams expose internal wiring, Deployment Diagrams bind software to hardware, and Profile Diagrams extend the notation with custom stereotypes. Behavior diagrams capture dynamics: Use Case Diagrams record what users need from the system, Activity Diagrams trace workflows step by step, State Machine Diagrams follow an object through its states, Sequence Diagrams order the messages between participants, Communication Diagrams show object interactions on a network, Timing Diagrams add time constraints to interactions, and Interaction Overview Diagrams connect multiple interaction fragments into a single control-flow view. Each type targets a specific modeling question in the development lifecycle.

When to Use Each UML Diagram Type

Class Diagrams: Reach for these during the design phase when you need to define object-oriented structures, field names, and data model relationships.

Use Case Diagrams: Pull these out during requirements gathering to capture what the system must do and which actors trigger each function.

Sequence Diagrams: Use these to map time-ordered API calls, authentication flows, and message exchanges between collaborating objects.

Activity Diagrams: Draw these to model business processes, multi-step workflows, and operations that can run in parallel.

State Machine Diagrams: Apply these whenever an object has a meaningful lifecycle with complex rules about which transitions are allowed.

Component Diagrams: Use these to plan high-level system architecture, microservice boundaries, and the units that will be independently deployed.

UML Diagram Best Practices for Software Teams

Scope each diagram to a single concern rather than cramming everything into one view. Follow UML notation conventions consistently so that any reader familiar with the standard can pick up your diagrams without a legend. Tailor the level of detail to the audience: executives benefit from high-level component diagrams, while developers working on an integration need granular class and sequence diagrams. Keep diagrams in version control alongside the code so they stay synchronized as the system evolves. Use color intentionally to highlight critical paths or distinguish subsystems, not just for decoration. Figviz applies these conventions automatically, producing notation-correct UML diagrams straight from a plain-text description.

How UML Helps in Research and System Design

Requirements analysis: Use case diagrams capture stakeholder goals before any design decisions are made, reducing costly late-stage changes.

Architecture documentation: Component and deployment diagrams record the system layout for onboarding new engineers and for compliance audits.

Algorithm design: Activity diagrams lay out complex computational steps and branching logic in a format that is easy to review and discuss.

Protocol specification: Sequence diagrams formalize how distributed components exchange messages, leaving nothing open to interpretation.

Database design: Class diagrams double as entity-relationship models, giving database engineers a head start on schema planning.

Research communication: Including UML diagrams in papers and theses makes software architectures reproducible and straightforward for peer reviewers to evaluate.

Frequently asked questions

Figviz provides a free UML diagram maker that turns a plain-text description into a standards-compliant diagram in seconds. Just explain your system architecture, your classes, or the interactions you want to capture, and the AI handles all the notation details. No manual drawing, no steep learning curve, and no cost to get started, making it practical for developers, architects, and students alike.

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