Heavy cream and whipping cream are both acceptable substitutes for creme fraiche. There are low-fat versions of creme fraiche, but these are not suitable to use in recipes that involve boiling, as the low-fat cream will separate.
When preparing a recipe that does not require boiling or high temperatures, full-fat sour cream is a substitute for creme fraiche. Half a cup of heavy cream and half a cup of sour cream can also serve as a creme fraiche substitute. However, it is ideal to add the sour cream as a garnish to the meal. Full-fat coconut cream is a vegan substitute for creme fraiche.