Benzyl-PEG4-Azido is widely used in bioconjugation and click chemistry applications. Its azido group enables efficient and selective reactions with alkynes via copper-catalyzed azide-alkyne cycloaddition (CuAAC), making it valuable for labeling biomolecules such as proteins, peptides, and nucleic acids. The PEG4 spacer enhances solubility and reduces steric hindrance, improving reaction efficiency in aqueous environments. This compound is particularly useful in drug delivery systems, where it facilitates the attachment of targeting ligands or therapeutic agents to carriers. Additionally, it is employed in the development of diagnostic probes and imaging agents, enabling precise tracking and detection in biological systems. Its versatility also extends to surface modification of materials, enhancing biocompatibility for biomedical applications.