5 Best Open-source Diagram Maker Tools

Draw.io is a powerful, free online diagramming application that provides extensive capabilities for creating professional-grade flowcharts, organizational charts, network diagrams, and complex visual representations. Its robust platform supports intricate diagram creation with an extensive library of shapes and templates.

1. Software Architecture: Designing system and network diagrams
2. Business Process Mapping: Workflow and organizational charting
3. Technical Documentation: Creating comprehensive visual guides

Deepnotes is a web-based collaborative workspace designed to create non-linear, interconnected notes and visual knowledge graphs. Its innovative approach allows users to build dynamic, spatial networks of information with intuitive linking and visualization capabilities.

1. Team Knowledge Management: Collaborative information mapping
2. Research and Documentation: Non-linear idea exploration
3. Project Planning: Complex interconnected brainstorming

Excalidraw is a free, web-based drawing tool that specializes in creating hand-sketched looking diagrams and collaborative visual representations. Its minimalist interface allows users to rapidly generate diagrams, wireframes, and conceptual sketches with a unique, organic aesthetic that mimics hand-drawn illustrations.

1. Rapid Prototyping: Quick visual concept development
2. Team Brainstorming: Collaborative ideation sessions
3. Technical Sketching: Simple system and workflow diagrams

Wireflow is a free, online tool designed for creating user flows and wireframes, specifically aimed at designers and developers needing to visualize user journeys. It offers an intuitive drag-and-drop interface that allows users to quickly map out flowcharts, wireframes, and simple prototypes without requiring advanced design skills. The focus is on ease of use and accessibility, making it ideal for fast iterations.

1. User Journey Mapping: Ideal for creating detailed user flow diagrams to visualize navigation and interactions.
2. Wireframe Design: Quickly build basic wireframes to outline screen layouts and components.
3. Team Collaboration: Perfect for collaborative design sessions, allowing multiple users to edit the same flow in real time.

Pencil is an easy-to-use, open-source tool for creating GUI prototypes and diagrams with drag-and-drop simplicity. It includes built-in stencils and templates for web and mobile interfaces, allowing users to quickly design and prototype without technical skills.

1. UI and UX Prototyping: Ideal for creating low-fidelity prototypes and wireframes for web and mobile apps.
2. Diagramming: Great for creating flowcharts, organizational charts, and other diagrams.
3. Design Collaboration: Excellent for teams needing to share and review mockups quickly across formats.