This review discusses the recent advancements in biopolymer-based hydrogel electrolytes for flexible supercapacitors. Biopolymers, such as polysaccharides and protein-based polymers, are highlighted for their natural abundance, low cost, biodegradability, and tunable morphology, making them suitable for sustainable energy storage devices. The review outlines the structure and characteristics of various biopolymers, their roles in gel electrolytes, and the mechanisms by which they enhance the electrochemical performance of supercapacitors. Key aspects include the energy storage mechanisms of supercapacitors, the performance evaluation standards of hydrogel electrolytes, and strategies to improve the mechanical properties and self-healing abilities of these materials. The review also addresses current technical challenges and potential solutions, emphasizing the importance of biopolymer-based hydrogel electrolytes in achieving high-performance, flexible, and sustainable energy storage systems.This review discusses the recent advancements in biopolymer-based hydrogel electrolytes for flexible supercapacitors. Biopolymers, such as polysaccharides and protein-based polymers, are highlighted for their natural abundance, low cost, biodegradability, and tunable morphology, making them suitable for sustainable energy storage devices. The review outlines the structure and characteristics of various biopolymers, their roles in gel electrolytes, and the mechanisms by which they enhance the electrochemical performance of supercapacitors. Key aspects include the energy storage mechanisms of supercapacitors, the performance evaluation standards of hydrogel electrolytes, and strategies to improve the mechanical properties and self-healing abilities of these materials. The review also addresses current technical challenges and potential solutions, emphasizing the importance of biopolymer-based hydrogel electrolytes in achieving high-performance, flexible, and sustainable energy storage systems.