Which is correct: 'pass-through' or 'passthrough' or 'pass through'? [closed]

You found all three on Google because all three are acceptable depending on circumstances.

As a guideline -

• use pass-through where it is an adjective before a noun (or sometimes an object-verbal noun compound such as egg-beater): They inspected the pass-through residue in the sediment trap.

• use passthrough as a noun, unless this makes it too long and cumbersome: He found a passthrough in the wall.

Pass through is two words: I saw him pass through a closed door.

The principle is to maximise clarity. A man eating shark and a man-eating shark are two very different things, but a Sunday morning service and a Sunday-morning service are not so you could leave out the hyphen in the latter.