Stitch width setting is a function on a sewing machine that determines how much the needle moves from side to side during sewing. This value is usually given in millimeters and is controlled by a dial or buttons. For a straight stitch, this function often changes the needle's position, shifting it from the center position further left or right, which allows sewing closer to the fabric edge. For other types of stitches, such as the zigzag stitch, or decorative stitches, this value directly affects their resulting width. A larger set value means a wider stitch, while a smaller value narrows the stitch.