Limit WooCommerce Product Quantity to One
Sometimes you might want to restrict customers of a WooCommerce site from purchasing more than one of any product. Fortunately this is made simple through use of the options already available in WooCommerce.
Simply edit the product in question, navigate to the ‘Inventory’ tab and tick the box labelled ‘Sold Individually’:
Once selected, the customer then will be unable to a) choose a quantity when adding the product to their cart, and b) will be unable to edit the quantity when viewing their cart.