Fluorobenzene probes for protein profiling through selective cysteine labeling have been developed by rational reactivity tuning. Tuning was achieved by selecting an electron-withdrawing para substituent in combination with variation of the number of fluorine substituents. Optimized probes chemoselectively arylated cysteine residues in proteins under aqueous conditions. Probes linked to azide, biotin, or a fluorophore were applicable to labeling of eGFP and albumin. Selective inhibition of cysteine proteases was also demonstrated with the probes. Additionally, probes were tuned for site-selective labeling of cysteine residues and for activity-based protein profiling in cell lysates.