What is the difference between fermented soy sauce and dark soy sauce?

Fermented soy sauce is made by inoculating soybeans (or defatted soybeans) and grains, such as wheat, with koji mold (a beneficial mold for the body), and then mixing them with salt water for fermentation and aging. It is similar to the soy sauce that was traditionally homemade, naturally fermented using microorganisms.

On the other hand, dark soy sauce was developed after Korea’s liberation to mass-produce soy sauce in a short period, leading to the creation of blended soy sauce.

Blended soy sauce is made by mixing fermented soy sauce with amino acid soy sauce or enzyme-hydrolyzed soy sauce.