Because they are generally very powerful oxidizing agents, most peroxyacids are prepared by electrolytic oxidation of ordinary oxyacids. Typically a high current density must be used to form the peroxyacid in good yield: the electrolysis of sulfuric acid being the most important example. Peroxy acids are generally not very stable in solution and decompose to ordinary oxyacids and oxygen, but relatively more stable anhydrous forms can be made by reacting hydrogen peroxide with chlorosulfonic acid or phosphoryl chloride.
All peroxy acids are very powerful oxidizing agents. Some such acids are peroxy-carboxylic acids, such as meta-chloroperoxybenzoic acid (mCPBA), which is used as a reagent in the Baeyer-Villiger oxidation and in oxidation of carbon-carbon double bonds in alkenes to generate epoxides (oxiranes). Sodium peroxy carbonate, Na2CO4, is widely used as a household bleaching agent for textiles, whilst sodium, potassium and ammonium peroxydisulfates (Na2S2O8, K2S2O8 and (NH4)2S2O8) are widely used as general purpose oxidizing agents in the laboratory.