We propose autocomplete for the design and development of virtual breadboard circuits using software prototyping tools. With our system, a user inserts a component into the virtual breadboard, and it automatically provides a user with a list of suggested components. These suggestions complete or extend the electronic functionality of the inserted component to save the user’s time and reduce circuit error. To demonstrate the effectiveness of autocomplete, we implemented our system on Fritzing, a popular open source breadboard circuit prototyping software, used by novice makers. Our autocomplete suggestions were implemented based upon schematics from datasheets for standard components, as well as how components are used together from over 4000 circuit projects from the Fritzing community. We report the results of a controlled study with 16 participants, evaluating the effectiveness of autocomplete in the creation of virtual breadboard circuits, and conclude by sharing insights and directions for future research.