A mask is a restriction on an edit for when blocks are placed e.g. only replace blocks below stone. Global masks apply to all edits, brush masks apply to just the current brush.

Use the name or id of a block (e.g. stone). For more info see this page on the block data syntax

Use ,(OR) or &(AND) to separate multiple masks. e.g. grass,$desert

Mask arguments should be inside square brackets e.g. #offset[0][5][3]

Perm: worldedit.global-mask Desc: The global destination mask applies to all edits you do and masks based on the destination blocks (i.e. the blocks in the world).

Perm: worldedit.global-mask
Desc: The global source mask applies to all edits you do and masks based on the source blocks (e.g. the blocks in your clipboard)

Perm: worldedit.brush.options.mask
Desc: Set the brush destination mask

Perm: worldedit.brush.options.mask
Desc: Set the brush source mask