Design system architecture, sequence lifecycles, flowcharts, ER diagrams, and Mermaid code in one unified workspace.
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Sequence Diagram
Lifelines, sync/async messages, return calls, activations, and notes.
🔀
Flowchart Maker
Process logic, decision diamonds, branch conditions, and algorithms.
🏗️
Architecture Diagram
Cloud stacks, microservices, caches, event buses, and network VPCs.
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ER Diagram
Relational database schemas, table columns, PK/FK, and 1:N relations.
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UML Class Diagram
Object models, interfaces, methods, visibility indicators, and inheritance.
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Mermaid Editor
Live Mermaid.js code editor with vector preview and instant export.
Start From a Template
My Saved Diagrams
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Export Diagram
Select the format you would like to download your diagram in:
Mermaid Source Syntax
Compatible with GitHub markdown, GitLab, Notion, and Mermaid CLI:
Diagram editing, layout calculations, SVG generation, PNG rendering, and local saves run entirely inside your browser. No diagram data or private architectures are uploaded to any server unless you are logged in and explicitly choose to save to your cloud account.
Diagram Studio — Developer Diagramming Workspace
Build, edit, and export software architectures, sequence flows, and system diagrams with Mermaid sync.
Runs in your browser
Free, no signup
Diagram Studio is a purpose-built workspace designed for software engineers, systems architects, and technical leads. Instead of fighting generic drag-and-drop tools or clumsy whiteboards, Diagram Studio gives you structured, type-safe diagramming tailored to developer workflows.
Switch seamlessly between Sequence Diagrams, Flowcharts, Cloud Architectures, Entity-Relationship Models, UML Class Diagrams, and code-first Mermaid markdown. Everything saves automatically to local storage with offline support, and exports directly to vector SVG, 2x retina PNG, and portable JSON.
How to use this tool
1Choose a diagram type from the studio sidebar or start immediately with one of the pre-built architecture templates (OAuth PKCE, Microservices, E-Commerce ER, CI/CD).
2Use the specialized component palette on the left to add actors, services, process nodes, database tables, or classes to your canvas.
3Inspect and customize elements using the properties panel on the right, or click "Source Code" to view and edit bidirectional Mermaid markdown syntax.
4Click "Export" to download crisp, infinitely scalable SVG vectors for documentation, retina PNGs for Slack and Jira, or ToolDuck project JSON backups.
Frequently asked questions
Can I use Diagram Studio without creating an account or logging in?
Yes. Diagram Studio works 100% anonymously out of the box. All your diagram projects, edits, and canvas settings are automatically persisted to your browser local storage. You only need to sign in if you want to sync projects to your cloud account across devices.
Is Diagram Studio compatible with Mermaid markdown syntax?
Yes. Diagram Studio features bidirectional Mermaid integration. You can generate standard Mermaid syntax from any visual diagram, paste existing Mermaid code into the editor, or use the dedicated Mermaid Editor mode for live code-first authoring.
Are my internal system architectures and API schemas private?
Yes. All diagram parsing, layout computation, SVG drawing, and PNG rendering are performed entirely inside your browser using client-side JavaScript. Private network topologies, tokens, and database schemas are never uploaded without explicit user action.
Which export formats are supported?
You can export diagrams as standalone SVG vector graphics (perfect for GitHub READMEs and technical documentation), high-resolution 2x retina PNG images, raw Mermaid source code, and reusable ToolDuck project JSON files.