Aminooxy-PEG3-azide is widely used in bioconjugation and chemical biology for its unique reactivity and water solubility. Its aminooxy group enables efficient conjugation with carbonyl-containing molecules, such as aldehydes and ketones, forming stable oxime linkages. This makes it valuable for labeling and modifying biomolecules like proteins, peptides, and antibodies. The azide group allows for click chemistry applications, particularly copper-catalyzed azide-alkyne cycloaddition (CuAAC), facilitating the attachment of additional functional groups or probes. The PEG spacer enhances solubility and reduces steric hindrance, improving reaction efficiency. This compound is particularly useful in drug delivery systems, surface functionalization, and the development of diagnostic tools, where precise and stable conjugation is critical.