Primarily used in papermaking, the production of cellulose pulp, and the manufacturing of soap, synthetic detergents, and synthetic fatty acids, as well as the refining of animal and vegetable oils. In the textile printing and dyeing industry, it is used as a desizing agent, scouring agent, and mercerizing agent for cotton fabrics. In the chemical industry, it is employed in the production of borax, sodium, formic acid, oxalic acid, phenol, etc. In the petroleum industry, it is used for refining petroleum products and in oilfield drilling mud. It is also utilized in the production of alumina, surface treatment of metallic zinc and copper, as well as in glass, enamel, leather, and dye industries. In the food industry, it serves as an acid neutralizer, a peeling agent for citrus fruits and peaches, a cleaning agent for empty bottles, cans, and other containers, and as a decolorizing and deodorizing agent.

When used as a basic reagent, it functions as a neutralizer, complex masking agent, precipitant, precipitation masking agent, absorber of small amounts of carbon dioxide and water, and a color developing agent for the determination of ketosteroids in thin-layer chromatography. It is widely applied in the manufacture of various sodium salts, soaps, pulp, finishing of cotton textiles, silk, and viscose fibers, regeneration of rubber products, metal cleaning, electroplating, bleaching, etc.

In cosmetic creams, sodium hydroxide saponifies with stearic acid and other substances to act as an emulsifier, used in the production of snow cream, shampoo, etc.