CMYK test page
One column per process ink, each a solid block over its own tint ladder, then the two- and three-ink overprints and a registration target in each ink.
Print at 100 per cent with margins set to none — the sheet carries its own 10 mm margin, and a second one from the browser is what makes a printer shrink the page.
The columns separate the cartridges
Keeping each ink in its own column means a fault has an address. A ladder that fades out at forty per cent in the magenta column and nowhere else is a magenta problem, and no amount of staring at a photograph would have told you that. Compare the four columns against each other rather than against what you expected — they share a print head and a paper, so the odd one out is the answer.
Overprints are the arithmetic check
Cyan over magenta should give a deep blue, cyan over yellow a green, magenta over yellow a red. A weak or shifted result names the ink that is short: a blue that leans purple is a cyan that is not laying down fully. The three-ink patch beside them is composite black, which on almost every printer comes out browner and duller than the patch of black ink next to it. That is expected, and it is why documents use black ink rather than three colours.
The last patch is rich black — full black ink with colour ink underneath. It should be visibly deeper than plain black. If it is not, the printer is already at its ink limit.
Registration, one ink at a time
The four targets are the same cross and the same rings drawn in each ink in turn. Printed on a healthy machine they are identical shapes in identical positions. A target whose rings are oval, or whose cross has a step where the arms meet, shows that one colour is being laid down out of step with the others — the fault that makes small coloured text look fringed.
Common questions
Is this a true CMYK test page?
The patches are stated as ink mixes wherever the browser supports device CMYK, so the request is unambiguous. What reaches the paper still passes through the print driver, which may convert it — no web page can bypass that.
Why does the three-ink black look brown?
Because real inks are not perfect filters. Cyan, magenta and yellow at full strength leave a muddy dark brown rather than a neutral black, which is exactly why a fourth, black ink exists.
My printer has six or more inks. Is this still useful?
Yes. The extra light cyan and light magenta tanks are used to build the pale end of the ladders, so a fault in them shows up as the top few steps of a column going wrong while the solid block below is fine.