The Fuzzy Select (Magic Wand) tool is designed to select areas of the current layer or image based on color similarity. It starts selecting when you click at a spot in the image, and expands outward like water flooding low-lying areas, selecting contiguous pixels whose colors are similar to the starting pixel. You can control the threshold of similarity by dragging the mouse downward or to the right: the farther you drag it, the larger the selected region. And you can reduce the selection by dragging upwards or to the left.

When using this tool, it is very important to pick the right starting point. If you select the wrong spot, you might get something very different from what you want, or even the opposite.

The Wand is a good tool for selecting objects with sharp edges. It is fun to use, so beginners often start out using it a lot. You will probably find, however, that the more you use it, the more frustrated you become with the difficulty of selecting exactly what you what, no more, no less. Perhaps the most frustrating aspect is that after you have released the mouse button, you can't make small adjustments to the threshold: you have to start over again from scratch. More experienced users find that the Path and Color Select tools are often more efficient, and use the Wand less. Still, it is useful for selecting an area within a contour, or touching up imperfect selections. It often works very well for selecting a solid-colored (or nearly solid-colored) background area.

Note that as the selected area expands outward from the center, it does not only propagate to pixels that touch each other: it is capable of jumping over small gaps. The distance it can jump over is set in the Tool Options page of the Preferences dialog: the "Default threshold" for Finding Continguous Regions. By raising or lowering this value, you can make the Magic Wand either more or less aggressive. (Filling with the Bucket Fill and Blend tools will also be affected.)