blockdiag Alternatives

UMLGraph is a professional automated drawing tool that allows the designers the declarative specification and drawing of UML class and sequence diagram.

yEd is a free desktop application to quickly create, import, edit, and automatically arrange diagrams. It runs on Windows, Mac OS X, and Unix/Linux.

Kimp is an unlimited design company, specializing in graphic design (including print and digital designs, custom illustrations, landing page designs and email designs) and video design.

Try for free Free Trial $599.0 / Monthly

Dia is a GTK+ based diagram creation program for GNU/Linux, MacOS X, Unix, and Windows, and is released under the GPL license.

Online diagramming application

Open Source

OmniGraffle is for creating precise graphics like website wireframes, an electrical system designs, or mapping out software class.

LucidChart is the missing link in online productivity suites. LucidChart allows users to create, collaborate on, and publish attractive flowcharts and other diagrams from a web browser.

ArgoUML, free and safe download. ArgoUML latest version: Open-source diagramming application for personal computers. ArgoUML is a program that allows users to create complex and professional diagrams.

UMLet - Free UML Tool for Fast UML Diagrams

StarUML

NClass is a free tool to easily create UML class diagrams with full C# and Java language support.

Gaphor is a Python-based, open source, multiplatform and multipurpose modeling application for creating nice UML diagrams for documentation.

Visualize, design, innovate. The ultimate diagramming and modeling suite for UML, ERD, BPMN, flowcharting and data architecture. Elevate your ideas to new heights.

freemium €59.0 / One-off (Standard Edition)

PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.

Open Source