Dark patterns are software designs that are used to manipulate and mislead users of an application or service. These patterns range from making it harder to end a subscription service, adding additional charges to a purchase, or having the user give out data or personal information. Prior work has explored perceptions of dark patterns, yet there is limited research exploring the effects of tooling to detect dark patterns on users. In this study, we introduce Dark Pattern Detector, a Chrome extension that would help users detect and understand dark patterns online. We conducted a technology probe study where participants (n = 40) were tasked with installing the extension and completing a series of tasks on different websites based on real-world Internet browsing. We leveraged mixed-methods surveys to collect feedback on dark pattern detection tools in practice. We found the majority of participants gave positive feedback, claiming they found the extension useful, interesting, and a good idea. Many participants also gave useful feedback about what changes or additions they would like to see in future systems. With our results, we provide implications to help users better understand dark patterns and motivate future tools for enhancing dark pattern detection in online environments.