The significance of usability testing in product development lies in its ability to evaluate how easily users can interact with a product or service. By conducting usability tests, developers gain insights into user behavior, identifying pain points and areas for improvement. This user-centered approach ensures that products are designed in alignment with real user needs and preferences, leading to higher satisfaction rates and better overall user experiences. Usability testing helps to reduce development costs by identifying issues early in the design process, thus avoiding costly revisions post-launch.