Structural equation modeling (SEM) is widely used in behavioral, social, and education research. Drawing publication-ready path diagrams for SEM is not a pleasant task with the existing software. The article introduces an open-source web-based graphical application, "semdiag," for drawing WYSIWYG SEM path diagrams interactively. The application is an on-going project developed by the authors using JavaScript, and it can be used in major web browsers, both online and offline. Several examples are provided to demonstrate how to use the application.