It is well known that some survey respondents reduce the effort they invest in answering questions by taking mental shortcuts – survey satisficing. This is a concern because such shortcuts can reduce the quality of responses and, potentially, the accuracy of survey estimates. This article explores “speeding,” an extreme type of satisficing, which we define as answering so quickly that respondents could not have given much, if any, thought to their answers. To reduce speeding among online respondents we implemented an interactive prompting technique. When respondents answered faster than a minimal response time threshold, they received a message encouraging them to answer carefully and take their time. Across six web survey experiments, this prompting technique reduced speeding on subsequent questions compared to a no prompt control. Prompting slowed response times whether the speeding that triggered the prompt occurred early or late in the questionnaire, in the first or later waves of a longitudinal survey, among respondents recruited from non-probability or probability panels, or whether the prompt was delivered on only the first or on all speeding episodes. In addition to reducing speeding, the prompts increased response accuracy on simple arithmetic questions for a key subgroup. Prompting also reduced later straightlining in one experiment, suggesting the benefits may generalize to other types of mental shortcuts. Although the prompting could have annoyed respondents, it was not accompanied by a noticeable increase in breakoffs. As an alternative technique, respondents in one experiment were asked to explicitly commit to responding carefully. This global approach complemented the more local, interactive prompting technique on several measures. Taken together, these results suggest that interactive interventions of this sort may be useful for increasing respondents’ conscientiousness in online questionnaires, even though these questionnaires are self-administered.