What is registration in printing?

Because each colour is laid down by a different unit, alignment has to be maintained across the whole run. Small registration marks are printed outside the trim area so the operator can check it at a glance, and modern presses adjust automatically within fine limits.

Registration is not only a press concern. It applies wherever two operations have to line up: die-cutting to the printed image, foil to its printed outline, embossing to the shape it is meant to lift, spot UV to the area it is meant to gloss. Those finishing passes happen on separate machines, so their tolerances are wider than colour-to-colour register on press.

That has a direct design consequence. A foil block that sits exactly inside a printed outline will show a sliver of the outline on one side if the sheet moves half a millimetre. Designs that need to survive normal variation either allow deliberate overlap or avoid butting two registered elements against each other at all — which is a better conversation to have at artwork stage than at proofing.

Registration accuracy on finishing is one of the in-process quality checks on every packaging run, and it is checked against the approved sample rather than by eye alone.