Mustard seems like a pretty cut-and-dry vegan item, since it is made from mustard plant seeds and doesn't seem to contain obvious animal-based ingredients. However, Healthline notes that not all of them may be suitable for a vegan diet.

Honey mustard is not acceptable for most vegan diets, as its foundational ingredients are honey and mustard, and honey is made by bees. Dijon mustard contains wine, and many wines are filtered through agents derived from animals like cows, chickens, and fish.

While some mustard varieties might be not entirely vegan-friendly, that's not the case generally, and most mustards are vegan-approved. If you’re a vegan, it’s always a good idea to make sure there aren’t any sneaky animal ingredients in the product.