As Visio is Microsoft's commercial solution for professional diagramming and workflow drafting, it has many alternatives just like other parts of the Microsoft Office Suite. These alternatives share many of the features found in Visio, such as support for scalable vector graphics files so that your charts and diagrams don't suffer any loss in quality when resized.
Osketch is a vector graphic design tool. It's lightweight, easy to use, and powerful. Osketch has many modern features. In Osketch, you can use any graphic as a mask, fill a shape with multiple modes, layout texts on a path...
CADE is a compact but powerful 2D vector editor for Windows. It includes basic Microsoft Office Visio functionality and could be used to create diagrams, network diagrams, flowcharts, schemas, maps and so much more.
Merge Plan is a user friendly diagram application. It is fully compatible with most diagram file formats. It is a great value in comparison to other diagram applications. It is part of Merge Soft Office.
Intelligent diagram visualization software. Quickly create professional diagrams. Create animated diagrams for Mobile viewers. Automatically animate the diagrams. Create 360° VR videos from diagrams. Manage related diagrams together.
Automatically generates cloud network topology diagrams for AWS, Azure and GCP. Visualizes cloud infrastructure, tracks versions, auto updates, generates compliance reports with on embed anywhere viewer and API access.
Elements.cloud is a free* cloud business requirements capture & business analysis / process mapping (UPN standard) app. *Free= for ever for everyone. Pro is aimed at highly regulated companies (Release Management/Version Control).