Ald-Ph-PEG4-Boc is a PEG-based linker for PROTACs which joins two essential ligands crucial for forming PROTAC molecules, and Ald-Ph-PEG4-Boc enables targeted protein degradation through the ubiquitin–proteasome system by facilitating effective ternary complex formation, thus advancing the design, optimization, and mechanistic study of next-generation protein degradation therapeutics in chemical biology and drug discovery workflows.