Free tool
DTF white ink checker
See which thin lines and tiny details lose their white underbase and print faded on dark shirts — at your real print size — and thicken them in one click. Free, no account, and nothing is uploaded.
Drop your design here or choose a file
A PNG with a transparent background works best. JPG and WebP work too. Your file stays on your device — nothing is uploaded.
Fine details you don’t want to lose?
A designer can redraw thin script and hairlines so they keep their look and still print on dark shirts — usually within a day.
Why thin lines print faded on dark shirts
Why the white shrinks
On a dark shirt every colour prints on top of a white underbase. Printer software pulls that white in from each edge — the choke — so it never peeks out as a white outline. On a bold shape you never notice.
Why thin lines fade
A line narrower than twice the choke has no white left under it at all. The colour lands straight on the dark fabric and looks dull, faded or disappears. A line only a little wider gets a sliver of white that breaks up.
Why print size matters
Lines shrink with the print. A 3-pixel outline is 0.25 mm on a 12″ back and 0.08 mm on a 4″ chest logo. The checker works in real millimetres at the width you choose.
How the fix works
Only the thin parts grow, outward and a pixel at a time, until they are wide enough to keep their white, taking the colour of the line. Bold areas stay exactly as they were. Loose specks too small to hold can be removed too.
How thin is too thin?
The limit depends on your printer’s choke. Below the first width a line has no white under it at all; below the second it keeps only a sliver.
| White choke | No white below | Safe from |
|---|---|---|
| 1 px (0.08 mm) | 0.17 mm | 0.37 mm |
| 2 px (0.17 mm) | 0.34 mm | 0.54 mm |
| 3 px (0.25 mm) | 0.51 mm | 0.71 mm |
At 300 DPI, 0.54 mm is about 6 pixels. Fine script fonts, thin outlines, hatching and small text in a light weight are the usual suspects.
How to check a design for white ink
- Drop in your PNG and choose the width you will actually print.
- Set the choke your printer software uses. If you don’t know it, leave it on Typical.
- Look for red (no white) and amber (thin white). Zoom in, or click “Zoom to a problem”, to see each one as it prints.
- Click “Fix my file” to thicken the thin lines and remove loose specks, compare, and download.
Questions
- Is the white ink checker really free?
- Yes. The check, the fix and the full-size download are all free, with no account and no watermark. It runs in your browser, so it costs us nothing to run.
- Is my design uploaded?
- No. Your design is checked and fixed on your own device, and the PNG is created there. Nothing is sent to our servers.
- What is white underbase choke?
- The amount your printer software shrinks the white layer in from each edge of the colour, so the white doesn't show as an outline around the design. Most DTF RIPs use 1–2 pixels at 300 DPI, about 0.1–0.2 mm. You'll find it in your RIP's white settings, often called choke, shrink or white spread.
- Do I need to worry about this on white shirts?
- Much less. On a white or light shirt a thin line with no white under it still shows, because the fabric behind it is light. The problem is dark and coloured shirts, where the colour needs white under it to look right.
- Will thickening change my design?
- Only the parts that are too thin, and only by as much as they need. Very fine script and hairlines get a little bolder; everything else is untouched. Zoom in on the preview and compare before you download.
- Can't I just lower the choke?
- Sometimes. A smaller choke keeps white under thinner lines, but makes a white edge more likely to show around the design if the film shifts. For one design with fine details, thickening the lines is usually the safer fix.
- What are the purple specks?
- Loose bits of ink smaller than about 0.5 mm. They hold too little adhesive powder and tend to peel off in the wash, so the fix can remove them.
Check the rest of your file with the free DTF file checker, or browse all free tools.