How does setting a donation option as the default in a charitable appeal affect people's decisions? In eight studies, comprising 11,508 participants making 2,423 donation decisions in both experimental settings and a largescale natural field experiment, the authors investigate the effect of "choiceoption" defaults on the donation rate, average donation amount, and the resulting revenue. They find (1) a "scale-back" effect, in which low defaults reduce average donation amounts; (2) a "lower-bar" effect, in which defaulting a low amount increases donation rate; and (3) a "default-distraction" effect, in which introducing any defaults reduces the effect of other cues, such as positive charity information. Contrary to the view that setting defaults will backfire, defaults increased revenue in the field study. However, the findings suggest that defaults can sometimes be a "self-canceling" intervention, with countervailing effects of default option magnitude on decisions and resulting in no net effect on revenue. The authors discuss the implications of the findings for research on fundraising specifically, for choice architecture and behavioral interventions more generally, and for the use of "nudges" in policy decisions.