How to Use the Magnetic Lasso Tool in Photoshop

Finding the Magnetic Lasso Tool

The Magnetic Lasso Tool is nested under the regular Lasso Tool. Click and hold the Lasso icon, or press Shift + L to cycle to it. Click once near an edge and then move the cursor along it; the tool lays down points that snap to the edge it detects, and Enter closes the selection.

Magnetic Lasso Tool Width

Width is how far from your cursor the Magnetic Lasso Tool looks for an edge. Press Caps Lock to see the width as a circle around the cursor. A large width (say 50 pixels) lets you trace loosely on a simple photo; a small width (around 5) keeps the tool from wandering when the subject is detailed or the background is busy. Put a point in the wrong place and Backspace or Delete removes the last one, so you can back up instead of starting over.

Contrast

Contrast sets how strong an edge has to be before the Magnetic Lasso Tool treats it as one. A crisp bird against a blurred background is high contrast, so a high value works there. A branch that blends into the background is low contrast, and lowering the value helps the tool find it, at the cost of picking up more noise elsewhere.

Frequency

Frequency controls how often the Magnetic Lasso Tool drops points. Raise it toward 100 for complicated shapes so the path is pinned down more often; lower it for smooth, simple edges. The three settings work together: high frequency plus a small width gives you tight control on a fiddly area.

Switch Lassos Mid-Selection

When the tool gets confused at the tip of a beak or along a soft edge, hold Alt (Option on Mac) and click to drop straight Polygonal Lasso points, or hold Alt/Option and drag to draw freehand with the regular Lasso. Release and the Magnetic Lasso takes over again. You can also click at any time to force a point exactly where you want one.

Finish the Magnetic Lasso Tool Selection on a Layer Mask

The selection doesn’t have to be perfect. Click the Add Layer Mask button to cut the bird out, add a solid color fill layer behind it, then refine: make a selection over a bad area, click the mask, and Edit > Fill with black to hide or white to reveal (Shift + Delete opens the Fill dialog). Lowering Density in the mask Properties lets you see through the mask while you work. For genuinely precise cut-outs, the Pen Tool is still the better choice.

Magnetic Lasso Tool Quick Reference

• Shift + L cycles to the Magnetic Lasso Tool.
• Caps Lock shows the Width as a circle around the cursor.
• Width small for detail, large for simple edges; Frequency high for complex shapes.
• Backspace / Delete removes the last point.
• Alt / Option + click for Polygonal, Alt / Option + drag for freehand Lasso.
• Fill the mask with black or white to fix the cut-out afterward.