The seaweed industry is a vital component of the marine economy in East and Southeast Asian coastal nations and is witnessing remarkable growth over the years. Global seaweed production surged from 10.6 million tons in 2000 to 35.82 million tons (fresh weight) in 2019, with a value exceeding $11 billion. Traditionally, seaweed finds applications in food (45–75%), hydrophilic colloids, and food additives. However, emerging markets in molecular gastronomy, dietary fiber, and prebiotics are paving the way for seaweed active substances like polysaccharides and oligosaccharides to become a prominent player in the future functional seaweed industry. Recent scientific research highlights the exceptional potential of algal polysaccharides as dietary fiber supplements due to their structural characteristics and indigestibility. Additionally, algal oligosaccharides possess unique antioxidant and probiotic effects, making them ideal for the growing health market. Technological advancements in polysaccharide and oligosaccharide production can lead to the production of diverse products catering to the emerging market needs. Guided by scientific support, the sustainable development of the seaweed industry thrives through functional advancements, guaranteeing the responsible utilization of seaweed resources.