ProcessOn: A Free and Easy-to-Use Online Flowchart and Mind Map Tool
ProcessOn is an online diagramming platform that allows users to create flowcharts, mind maps, UI prototypes, UML diagrams, network topology maps, organizational charts, and more directly in the browser without installing any client software.

Registration Link: https://www.processon.com/
Getting Started
ProcessOn offers a wide variety of ready-made templates that users can select and modify as needed, making it very simple to get started.

For professional users or complex projects where built-in templates may not suffice, users can create new files from scratch. The platform provides a large library of icons, allowing for the creation of beautiful and comfortable flowcharts, as shown in the screenshot below (click to enlarge).

ProcessOn also supports file sharing, real-time collaborative editing, and multiple version history features.

The image below shows a blog architecture diagram created by xiaoz using ProcessOn.

ProcessOn Limitations
The free version of ProcessOn allows users to save up to 9 files. Completing your personal profile information adds 5 more slots, and successfully inviting one friend adds an additional 3 files.

Summary
ProcessOn is easy to use and produces aesthetically pleasing flowcharts, making it convenient for both individual and team use.
ProcessOn Official Website: https://www.processon.com/