Overprint and knockout explained
When one coloured object sits on top of another, the press needs to know: cut the bottom colour out (knockout), or print the top colour over it (overprint)? The default is knockout. But overprint has important uses — and getting it wrong is a classic prepress disaster, with objects vanishing or colours shifting on press.
Knockout: the default
By default, a top object 'knocks out' the area beneath it — the press leaves a hole in the lower colour exactly the shape of the object, so the two inks don't mix. Print yellow text on a cyan background as knockout and the cyan is removed under the letters, so they print as pure yellow on the paper. This is what you want almost all the time.
Overprint: printing on top
Set an object to overprint and the press prints it over the colour beneath, with no knockout — so the inks combine. Overprint that same yellow text on cyan and you get green, because yellow over cyan mixes. Used deliberately, overprint is useful; used by accident, it produces unexpected colours or makes light objects disappear into dark backgrounds.
The danger case
A common disaster: a white object accidentally set to overprint. White is the absence of ink, so 'white overprinting' means nothing prints — the object simply vanishes into whatever is beneath it. Always check that white and light elements are set to knockout.
Why black text usually overprints
There's one place overprint is the correct default: small black text. If 100% black type knocks out, any tiny misregistration leaves a thin white halo where the knockout hole doesn't line up with the letters. Setting black to overprint removes the hole — the black simply prints on top of the background, and small registration shifts become invisible. Most workflows automatically overprint 100% K text for exactly this reason. (Rich black is different — see rich black vs pure black.)
Checking overprint before you send
Overprint settings are invisible on a normal screen — the file looks fine and only goes wrong on press. Protect yourself:
- Turn on Overprint Preview (Acrobat, InDesign, Illustrator) to see what will actually happen.
- Check that white and light-coloured objects are not set to overprint.
- Confirm 100% K text overprints, but rich black panels knock out.
- Where inks overlap by design, watch the combined ink coverage doesn't exceed the limit — the TAC checker helps.
Frequently asked questions
What's the difference between overprint and knockout?
Knockout removes the colour beneath an object so the inks don't mix (the default). Overprint prints the object on top of the colour beneath, so the inks combine. Knockout keeps colours pure; overprint mixes them.
Why is my white text disappearing in print?
It's almost certainly set to overprint. White means no ink, so overprinting white prints nothing — the text vanishes into the background. Set white and light objects to knockout, and use Overprint Preview to catch it before output.
Should black text be set to overprint?
Yes, small 100% K black text is usually best overprinting. It avoids thin white halos from misregistration around the knockout. Large rich-black panels, however, should knock out and be built as a proper rich black.
How do I check overprint settings?
Use Overprint Preview in Acrobat, InDesign or Illustrator to simulate how overprints will actually print. It reveals vanishing objects and unexpected colour mixes that look fine in normal view but go wrong on press.
Turn on overprint preview
Overprint problems are invisible until the press proves them — a white object set to overprint just vanishes. We preview every file with overprint on, and it's saved us more than once. Reviewed June 14, 2026.