Antibody Internalization Detection Reagent enables real-time live-cell monitoring of human IgG endocytosis. Conjugated to a pH-sensitive fluorescent dye, its anti-human Fc moiety binds IgG Fc regions specifically. Minimal extracellular fluorescence and acid-triggered signal amplification in endosomes/lysosomes ensure low background and reliable quantification, supporting research of ADCs and in vivo cell therapy.