Sites and apps similar to Vellum Diagram Editor include draw.io, which is free and open source. Other options are Excalidraw, LibreOffice - Draw, yEd Graph Editor and Dia. You're spoiled for choice with Diagram Editors like Vellum Diagram Editor: we list more than 50 alternatives for Windows, Mac, Linux, iPad and Android.
Lightweight, powerful, easy to use, UML tool
Software Ideas Modeler is a lightweight and powerful CASE tool. It supports UML 2.2 diagrams and a lot of other ones. Software Ideas Modeler is freeware (for non-commercial use). Commercial user may use this software only after buying.
Slovakia
EU
Apple Vision like gesture controls meet ChatGPT in an app to explore knowledge that doesn't require a headset or downloads. You just need a modern device with a webcam.
PGF/TikZ is a tandem of languages for producing vector graphics from a geometric/algebraic description. PGF is a lower-level language, while TikZ is a set of higher-level macros that use PGF. The top-level PGF and TikZ commands are invoked as TeX macros, but in contrast with...
ARIS Express is based on the proven ARIS methodology and industry standards. Its intuitive user interface and the latest improvements in modeling assistances enable instant results. This free version will appeal to universities and vocational schools, as well as BPM beginners...
GermanyEU
Core2D is a multi-platform application for making data driven 2D diagrams. The application has built-in wyswig vector graphics editor where you can bind data to shapes, share data across multiple documents, edit documents using layers.
PolandEU
Grapholite is a powerful online solution for the creation of flowcharts, org charts, mind maps, Venn charts, web site structures, etc. Can be used online and offline
Ukraine
MagicDraw is an award-winning business process, architecture, software and system modeling tool with teamwork support. MagicDraw UML can do comprehensive UML diagramming, reverse and forward engineering for Java and C++.
ConceptDraw DIAGRAM v14 is the only product that supports Visio legacy, runs on macOS and Windows, and is a perpetual license. Import/Export VDX, VSDX, VSSX and Import VSD, VSS files.
Ukraine
TouchDraw is a vector drawing application that gives you everything you need to create structured 2D vector graphics such as flow charts, graphs, diagrams, illustrations, logos and floor plans just to name a few.
United States
Vecta is a cloud-based collaborative diagramming tool that boosts productivity and increase effectiveness for team communication.
Flowsage is a web-based application that simplifies flowchart creation using AI technology, helping you visualize ideas efficiently and intuitively.
United Kingdom