Deselect a selection

Command + D

Reposition marquee while selecting

Spacebar-drag

Add to or subtract from a selection

Any selection tool + Shift or Option-drag

Intersect a selection

Any selection tool + Shift + Option-drag

Constrain marquee to square or circle (if no other selections are active)

Shift-drag

Draw marquee from center (if no other selections are active)

Option-drag

Constrain shape and draw marquee from center

Shift + Option-drag

Switch to Move tool

Command (except when Hand or any shape tool is selected)

Switch from Magnetic Lasso tool to Lasso tool

Option-click and drag

Delete last anchor point for Magnetic or Polygonal Lasso tool

Delete

Apply/cancel an operation of the Magnetic Lasso tool

Enter/Esc

Move copy of selection

Move tool + Option-drag selection

Move selection area 1 pixel

Any selection + Right Arrow, Left Arrow, Up Arrow, or Down Arrow

Move selection 1 pixel

Move tool + Right Arrow, Left Arrow, Up Arrow, or Down Arrow

Move layer 1 pixel when nothing selected on layer

Command + Right Arrow, Left Arrow, Up Arrow, or Down Arrow

Increase/decrease detection width

Magnetic Lasso tool + [ or ]

Accept cropping or exit cropping

Crop tool + Enter or Esc

Toggle crop shield off and on

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