Microsoft Office Visio, draw.io, Lucidchart, Mermaid, OmniGraffle, PlantUML, Google Drawings, yEd Graph Editor, Graphviz, ArgoUML, WhiteStarUML, LibreOffice - Draw, astah Community Edition, SequenceDiagram.org, BPMN Sketch Miner, Gaphor, WebSequenceDiagrams, BOUML, GenMyModel, jsUML2, Cubetto, Poseidon for UML, Wireflow, TopCoder UML, Oqto Diagram, Chrons Web Modeler, Classbuilder, Syngraph.me, ckwnc, SEQO, yUML are some alternatives to PlantText.