Supercapacitor technology is one of the most flourishing renewable and sustainable energy supports that satisfactorily addresses the sky-rising demands of nonstop power supply. However, corresponding currently available supercapacitors/ ultracapacitors primarily lack adequate energy densities besides high fabrication costs, adaptability, and other technical problems, such as high self-discharge rates, resulting in short-term energy storage, that limit their boundless commercialization. Various strategies have been adopted for upgrading these devices’ energy performances that include the essential need for extended potential window which can be reasonably accomplished through appropriate choice of electrolytes, along with judicious electrode material designing. Rightly, electrolytes have turned out to be an imperative “performance-dictating” constituent in the electrochemical energy storage systems. The electrolytes are also crucial for ensuring device thermal stability, internal resistances, controlling self-discharges, durability, etc. They have been traditionally used in liquid forms such as aqueous, nonaqueous/organic, ionic liquids for high-performing supercapacitors. This chapter provides an outline of the latest advancements of popular liquid-based electrolytes employed in various supercapacitors. The basic ideas for scheming and optimizing electrolyte characteristics considering their production cost, availability, and environmental benignity have also been highlighted. Conclusively, some propositions have been put forward that might be handful in overcoming the current challenges faced without compromising with the existing benefits.