Spatially resolved techniques for exploring the molecular landscape of tissue samples, such as spatial transcriptomics, often result in millions of data points and images too large to view on a regular desktop computer, limiting the possibilities in visual interactive data exploration. TissUUmaps is a free, open-source browser-based tool for GPU-accelerated visualization and interactive exploration of 107+ data points overlaying tissue samples. TissUUmaps 3 provides instant multiresolution image viewing and can be customized, shared, and also integrated into Jupyter Notebooks. TissUUmaps introduces new modules where users can visualize markers and regions, explore spatial statistics, perform quantitative analyses of tissue morphology, and assess the quality of decoding in situ transcriptomics data. Thanks to targeted optimizations the time and cost associated with interactive data exploration were reduced, TissUUmaps 3 is enabled to handle the scale of today's spatial transcriptomics methods. TissUUmaps 3 provides significantly improved performance for large multiplex datasets as compared to previous versions and we envision TissUUmaps to contribute to broader dissemination and flexible sharing of large scale spatial omics data. https://www.sciencedirect.com/science/article/pii/S2405844023025136?via%3Dihub