INCI name
Sodium Hyaluronate
Also listed as: The sodium salt of hyaluronic acid
Sodium hyaluronate is the sodium salt of hyaluronic acid, a large sugar molecule that holds water. The salt dissolves more easily in water than the acid form, so it is the name you will usually see on a serum label.
The ingredient can be made by bacterial fermentation, which is now the usual cosmetic source, or historically from animal tissue such as rooster combs. A vegan claim depends on the source, not on the INCI name.
Molecular weight varies. Lower-weight grades are marketed as penetrating further; higher-weight grades form a surface film that feels slippery and moist. The label almost never states the weight.