In this article, I will be listing some of the top tools for drawing ER diagrams online. Priority will be given to ease of use, user experience, and functionality. An entity relationship diagram, or ER Diagram (ERD), is a visual model of your database schema. It describes the database structure and helps conceptualize how pieces of data interact with one another across a robust database. To some extent, ER diagrams look like flowcharts; they show the database tables as rectangles, with connecting lines representing the relationships between tables through primary and foreign keys.