Azido-PEG9-alcohol is widely used in bioconjugation and chemical biology due to its azide functional group, which enables click chemistry reactions, particularly with alkynes. It serves as a versatile linker in the synthesis of complex molecules, such as drug delivery systems, where it facilitates the attachment of therapeutic agents to targeting moieties. Its PEG (polyethylene glycol) spacer enhances solubility and reduces immunogenicity, making it suitable for biomedical applications like protein modification, antibody-drug conjugates, and surface functionalization of nanoparticles. Additionally, it is employed in the development of hydrogels and biomaterials for tissue engineering, where its biocompatibility and reactivity are advantageous.