A sheet feeder includes a cassette has a sheet container space configured to hold a sheet having a wireless tag. The cassette feeds the sheet to a first side in a first direction. A horizontal direction orthogonal to the first direction is a second direction. A range in the second direction occupied by the wireless tag of the sheet held in the sheet container space is a first range. A range in the second direction including at least a part of the first range is a second range. A range in the second direction occupied by the sheet container space is a third range. In the cassette front wall, a height in a vertical direction in the third range except the second range is smaller than a height in the vertical direction in the second range.