The purpose of this article is to introduce a new tool—the Open Science Online Grocery—for studying the effects of the choice context on purchasing decisions. We first review the features of the tool: a mock online grocery store containing over 11,000 products wherein researchers can modify the choice context (e.g., positioning, labeling, suggestions) and observe resulting choice. Then, we present three studies illustrating how the tool can help assess how changes to labeling, ordering, and positioning affect choice. We find that both ordering and positioning have significant effects on choice while labeling does not. These findings largely align with existing research in field and laboratory settings. We hope this tool proves useful to researchers wanting to test choice context modifications in a relatively affordable and efficient manner.