Class Diagram Maker

• Free online UML class diagram maker that builds diagrams quickly through visual forms, supporting 6 relation types (inheritance, composition, aggregation, association, dependency, realization) with real-time Mermaid rendering
• Class management: add multiple classes, each holding attributes (visibility public/private/protected/package, name and type) and methods (with parameters and return type), all addable and removable in one click
• Relationship management: pick a source and target class, a relation type and an optional label; switchable examples, 5 themes, zoom (25%–300%) and fullscreen, plus the option to view and copy the generated Mermaid code
• One-click export to SVG or high-res PNG (2×); everything runs locally in your browser — nothing is uploaded

1. Open the tool page — no download or installation needed; a sample class diagram loads automatically
2. In class management click "Add Class", give it a name, then add attributes and methods for the selected class (also switch classes from the chips at the top and delete when needed); the preview updates in real time
3. In relationship management click "Add Relationship" (at least two classes are required), choose the source → target classes, a relation type, and optionally a label
4. Switch examples, theme, zoom and fullscreen as needed, or click "View Code" to copy the generated Mermaid code; when done, click "Download" and pick SVG or PNG to export

• This tool is completely free and requires no sign-up
• Everything runs locally in your browser — nothing is uploaded
• Adding a relationship requires at least two classes; a class with no name shows as "Unnamed Class", so naming classes first helps relationships connect and display correctly

Free online UML class diagram maker. Quickly create class diagrams via visual forms, supporting classes, attributes, methods, inheritance, composition, aggregation, association and more. Real-time preview and one-click SVG/PNG export.

Open the tool page — no download or installation needed; a sample class diagram loads automatically In class management click "Add Class", give it a name, then add attributes and methods for the selected class (also switch classes from the chips at the top and delete when needed); the preview updates in real time In relationship management click "Add Relationship" (at least two classes are required), choose the source → target classes, a relation type, and optionally a label Switch examples, theme, zoom and fullscreen as needed, or click "View Code" to copy the generated Mermaid code; when done, click "Download" and pick SVG or PNG to export

This tool is completely free and requires no sign-up Everything runs locally in your browser — nothing is uploaded Adding a relationship requires at least two classes; a class with no name shows as "Unnamed Class", so naming classes first helps relationships connect and display correctly

Yes, Class Diagram Maker is completely free. No download or installation required — it runs right in your browser.