I choose Diagrams.net formerly known as draw.io (current URL: https://app.diagrams.net/)!

Diagrams.net 

Quoted from ChatGPT:

Diagrams.net (formerly draw.io) is a free, versatile diagramming tool developed by JGraph Ltd that runs in your browser or as a desktop app for Windows, macOS, Linux—and even via containers (en.wikipedia.org).

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🔄 Why the name change from draw.io to diagrams.net?

• In February–March 2020, JGraph officially began migrating its web app from the draw.io domain to diagrams.net due to security concerns over the .io domain and its control (drawio.com).

• They assured users that the software, files, integrations (like Confluence, Jira, GitHub, etc.), and user experience remain the same—only the domain changed .

• Many still refer to it as “draw.io,” and that branding persists in the desktop apps and APIs (github.com).

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What it does

• Create flowcharts, UML, org charts, ER diagrams, network maps, mind‑maps, etc. (en.wikipedia.org).

• Works online, offline (via Electron desktop app), and integrates with Google Drive, OneDrive, Dropbox, GitHub, GitLab, and tools like VS Code, Confluence, Jira, Notion, and more .

• Export to PNG, JPEG, SVG, PDF, and import Visio files (VSDX) (en.wikipedia.org).

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Who uses it?

• Widely popular in tech circles, often compared to Visio, Lucidchart, SmartDraw (en.wikipedia.org).

• Loved by sysadmins, developers, network engineers—because it’s powerful yet free, with tight cloud integrations .

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So... should you use draw.io or diagrams.net?

Both are exactly the same tool.

• Use diagrams.net, the official and secure domain.

• You can still call it draw.io—just don’t worry about confusing branding.

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Quick Tips 💡

• Visit https://app.diagrams.net to start right away—no sign‑up or login needed.

• If you're more comfortable thinking "draw.io," go right ahead—it’s the same experience.

• For integrations (e.g. embedding in Confluence/Jira), the domains draw.io, app.diagrams.net and embed.diagrams.net all work seamlessly—they just redirect behind the scenes (drawio.com).

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In summary

• diagrams.net = secure, official domain.

• draw.io = well-known brand name that still lives on.

• Software, features & integrations stay identical.

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Diagrams.net (formerly draw.io) is 100% free to use

✅ Free Features:

• No account required.

• No time limits or usage caps.

• Works online (via browser) or offline (via downloadable desktop app).

• Save diagrams to:

  • Your device

  • Google Drive, OneDrive, Dropbox, GitHub, etc.

• Export to PNG, JPEG, SVG, PDF, and more.

• Open-source codebase (on GitHub).

💼 Paid Options (Optional):

• Paid versions are available only when integrated with Confluence or Jira via Atlassian Marketplace (for enterprise/business use).

  • These charge per user—but only because of Atlassian's pricing system.

👉 For individual users, students, educators, developers, and small teams:
Everything is free. No watermark. No forced login. No trial period.