There are many differences to consider when comparing fill dirt versus topsoil. Fill dirt is a mix of sand, clay, and rock fragments and is usually the layer found under topsoil. It doesn’t contain any organic matter or fertilizer. It’s more stable than topsoil and is great for filling holes, leveling land, and securing the area around retaining walls.
You can buy filtered fill dirt or regular fill dirt—the former can cost more but it won’t contain any debris. In comparison, topsoil contains organic matter and minerals. It’s nutrient-rich and works well in garden beds, lawns, and other forms of landscaping. It’s usually darker in color than fill dirt and costs more. It’s also less stable than fill dirt as it will settle or erode over time.