The City–Region Explorer is a user-friendly, web-based tool to help policymakers and planners visualize and analyze how people connect to urban centers across the globe. It uses travel-time data to define city–regions that reflect real-world access to services and opportunities. By integrating geospatial and socioeconomic layers, the Explorer helps identify underserved areas, guide infrastructure investments, and design inclusive development strategies. The tool supports a wide range of applications, including assessing agricultural potential, planning rural connectivity, mapping poverty and food insecurity, analyzing education access, monitoring natural resource pressures, and designing polycentric development corridors. Its intuitive interface and global coverage make it a valuable asset for advancing equitable, evidence-based planning in support of the Sustainable Development Goals.