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Chemoproteomic probes serve as valuable tools to study and perturb protein function on a global scale. Despite advances in methodologies for cysteine and lysine profiling, a large fraction of the human proteome remains inaccessible with current activity-based probes. Here, we describe development and application of sulfur-triazole exchange (SuTEx) chemistry for developing covalent probes with broad applications for chemical proteomics. We show modifications to the triazole leaving group can produce sulfonyl probes with high chemoselectivity for tyrosines over other nucleophilic amino acids to investigate thousands of tyrosine sites in lysates and live cells. We discover hyper-reactive tyrosines are enriched in enzymatic, protein–protein interaction and nucleotide recognition domains. We apply SuTEx as a chemical phosphoproteomics strategy to monitor activation of phosphotyrosine sites. Our findings illustrate the broad potential for deploying SuTEx to globally investigate tyrosine reactivity, function and post-translational modification state in complex biological systems.