In an era of heightened consumer awareness and intense competition, public libraries must prioritize service quality, user satisfaction, and loyalty. Traditional methods of gauging user feedback, such as surveys and interviews, are time-consuming and resource-intensive. With the advent of big data and the proliferation of mobile internet, users now express their opinions through social media platforms like Instagram and Facebook and review platforms like Google Maps. This study compares public library service feedback from social media and Google Maps reviews in Taiwan’s six municipalities. The Keypo big data analysis system and web scraping techniques categorized feedback using the LibQUAL+ model: Library as Place, Affect of Service, and Information Control. The comparative analysis revealed significant differences in the nature and focus of feedback across platforms. Social media feedback was more detailed and service-oriented, while Google Maps reviews focused on physical amenities and resource availability. These findings suggest that public libraries can benefit from a dual approach to feedback collection, leveraging both social media and review platforms to gain comprehensive insights into user opinions and enhance service quality.