Top Free Diagramming Tools Every Engineer Should Know

1. Excalidraw

Excalidraw is an open‑source virtual whiteboard that lets you draw flowcharts, diagrams, and sketches in a hand‑drawn style. It supports multiple languages, including Chinese, offers a rich library of third‑party assets, real‑time collaboration, keyboard shortcuts, and can import tables from Excel. Features include a clean interface, no registration required, end‑to‑end encryption, and shareable web links.

https://excalidraw.com/

2. Zen Flowchart

Zen Flowchart is an English‑language online tool that is easy to use thanks to built‑in browser translation. After a quick email registration you can log in and start creating diagrams. Its product highlights include simple online flowcharts, mind maps (Zen Mind Map), low‑fidelity wireframes, a free online whiteboard for real‑time brainstorming, task management (Zen Task), and collaborative notes (Zen Notes).

https://www.zenflowchart.com/

3. Visual Paradigm Online

Visual Paradigm Online provides a wide range of templates for flowcharts, UML, BPMN, ArchiMate, and more. It includes multi‑functional design tools such as an infographic editor, e‑book editor, chart editor, and collage maker. The platform also offers PDF tools, design editors, resource libraries, free e‑book publishing, chart creation, photo editing, real‑time collaboration, form builders, and spreadsheet editors.

https://online.visual-paradigm.com/cn/

4. draw.io (diagrams.net)

draw.io is a widely‑used, cross‑platform diagramming solution available on Windows, macOS, and the web. It supports a variety of diagram types, including network topologies, and offers real‑time collaboration.

https://www.draw.io/ or https://www.diagrams.net/

draw.io can also create attractive network topology diagrams.

5. Liuchengtu (迅捷画图)

Liuchengtu is a Chinese‑made diagramming tool with many ready‑made templates. While the interface is user‑friendly, many premium templates require payment.

https://www.liuchengtu.com/

Key features include multi‑format import/export, real‑time multi‑user editing, cross‑platform support, offline editing, customizable shapes and lines, automatic cloud sync, one‑click sharing with password protection, version history, and more.

6. ProcessOn

ProcessOn is an online collaborative drawing platform that supports flowcharts, mind maps, org charts, network topologies, BPMN, UML, UI prototypes, and iOS mockups. It enables real‑time collaboration and sharing via the internet.

https://www.processon.com/

Which tool do you use now, and do you have other recommendations?