Introduction “In a world where mobile has become our primary device, marketers should think about mobile as a sound off environment, where users hate being interrupted with sound.” －Caroline Hugonenc (2019), Global VP Research & Insights at Teads.tv The soundless video ad is the new trend online ad that received little attention (Campbell & Pearson, 2019). Facing the new trend of soundless video ads, this research aims to explore how to improve consumers’ attitudes toward soundless video ads by manipulating subtitle. Drawn on process fluency theory (Reber et al., 2004), this research aims to answer three research questions to help practitioners design effective soundless video ads. RQ1: Can adding subtitle to a soundless video advertisement (ad) increase consumers’ positive attitude? RQ2: Does the font type of subtitle influence consumers’ attitude? RQ3: Does the interaction effect of font type and subtitle position influence consumers’ attitude?

• Jung-Kuei Hsieh(National Taipei University, Taiwan)