draw.io

draw.io is a free, open-source diagramming tool that lets you create flowcharts, network diagrams, UML charts, wireframes, and more — without creating an account or paying a cent. You can use it in the browser or via the desktop app, and you choose where your files are stored: Google Drive, OneDrive, GitHub, or locally. The company never sees your data.

Two things make draw.io stand out: backwards compatibility and real-time collaboration. Those old diagram files from 2005? They still open perfectly. Team members can edit the same diagram at the same time with visible cursors. It's also deeply integrated with popular platforms — Confluence, Jira, VS Code, Notion — so you can work inside your existing tools rather than bouncing between apps. The entire codebase is Apache 2.0 licensed, and the company is independently owned, so there's no pressure to upsell or monetize your data.

Who benefits most? Software engineers designing system architectures, project managers mapping processes, educators creating class materials, and anyone who needs clear visual communication without the hassle of subscriptions or compatibility headaches. It's the kind of tool that quietly does its job well — and has been doing it for 20 years.