# DTF image checker: is my file ready to print as a DTF transfer?

A free DTF image checker: choose a PNG, JPEG or WebP and see whether it is ready to print as a DTF transfer: its transparent background, half-transparent areas, light halo, stray specks, resolution at your print size and file format, each with the number behind it. Nothing is uploaded.

**An image is ready to print as a DTF transfer when it is a PNG with a fully transparent background, no half-transparent areas beyond the smoothing along its edges, no light fringe or stray specks round the design, and 300 DPI at the size it prints: 3307 pixels across for a 28 cm wide print.** Choose an image and the checker reads it in your browser, then says, check by check, what passes, what to look at and what to fix, with the number behind each. Nothing is uploaded.

## How to use it

1. **Choose the image.** A PNG, JPEG or WebP of up to 50 million pixels, which your browser reads without sending it anywhere. Or check one of the two samples.
2. **Enter the print width.** The width the design prints at, in centimetres or inches. It starts at 28 cm, the front print area of the t-shirt that comes with PrintBlob.
3. **Read each line.** Each check says Pass, Warning or Fail, with the number it is decided on and what to do about it.
4. **Fix the file and check it again.** Make the changes in your image editor, export a PNG with its transparent background kept, and choose it again.

## How each check works

The rules are those [DTF print file requirements](/guides/dtf-print-file-requirements/) sets out, with the light halo from the sources below. Where the checker draws a line between pass, warning and fail, the line is the checker’s own, and each is given here.

- **Transparent background.** DTF prints everything in the file that is not fully transparent, with white ink behind it, so a background prints as a box. The checker counts the fully transparent pixels along the image’s four edges: at least 50% passes, fewer is a warning, and none at all, or no transparent pixel anywhere, fails.
- **Half-transparent areas.** A pixel that is partly see-through has no clear answer on a DTF printer: a soft shadow, glow or fade can print as a solid block, a pale haze or not at all. The thin smoothing along the edges of text and shapes is normal, so a half-transparent pixel within 2 pixels of both a fully opaque and a fully transparent pixel is left out. Under 0.1% of the artwork’s pixels passes, up to 1% is a warning, and more fails.
- **Light halo.** Removing a white background often leaves a ring of near-white pixels round the design, which prints as a light outline. The checker looks at the artwork’s outline, its pixels within 2 pixels of a transparent one, and counts those that are near-white (red, green and blue each at least 230 of 255) beside solid, darker artwork; white artwork is not a halo. Under 1% of the outline passes, up to 5% is a warning, and more fails.
- **Stray specks.** A dot left far from the design prints as a dot of ink, and small isolated dots are the first parts of a transfer to break or lift. The artwork is the largest shapes that together hold 99% of the image’s visible pixels; a shape wholly outside their bounds and under 1 mm at the print size, the top of the 0.5 to 1 mm printers commonly ask for, is a stray speck. Any is a warning: remove it unless it is meant.
- **Resolution at your print size.** The image’s width in pixels divided by the print width in inches. 300 DPI or more passes; from 150 DPI it is a warning, sharp enough but below 300; below 150 the print is visibly soft, and it fails. The [image print size calculator](/tools/print-size/) shows the largest size an image prints at, at either resolution.
- **File format.** Read from the file’s first bytes, not its name. PNG passes. JPEG fails, because it cannot be transparent. WebP and other formats are a warning: DTF printers ask for PNG.

The DPI value written in the file (a PNG’s pHYs chunk, a JPEG’s JFIF or Exif header) is shown apart. It changes no pixel and so no sharpness: a file marked 72 DPI with enough pixels prints as well as the same file marked 300.

## The two samples

The print-ready sample is the print file PrintBlob Pro made of the sunset design on this site’s home page, 3307 pixels across for the 28 cm front of the bundled t-shirt. The sample with problems is made from it: shrunk to too few pixels, with a near-white fringe round the sun, a soft shadow under the words and four stray specks in the corners. It still says 300 DPI, which changes none of that.

## Large images

The checker reads up to 50 million pixels, such as a 6000 × 6000 pixel PNG, a strip at a time in the background, so the page keeps responding while it works. A larger image is refused before it is opened; check a smaller export of it.

## Questions

### How do I know if my image is good for DTF printing?

It is a PNG with a fully transparent background, it has no half-transparent areas beyond the smoothing along its edges, no light fringe round the design and no stray specks, and it has 300 DPI at the size it prints, which is its width in pixels divided by the print width in inches. The checker tests each of these in your browser and gives the number behind each.

### Why does my DTF transfer have a white outline round it?

Usually because the background was removed from a white background and left a ring of near-white or half-transparent pixels round the design. DTF prints every pixel that is not fully transparent, with white ink under it, so the ring prints as a light outline. The light halo and half-transparent checks find it; remove the ring with a clean selection, or contract the selection by a pixel or two and delete again.

### Does the DPI in my file need to say 300 for DTF printing?

No. The DPI value saved in a file changes no pixel. What decides sharpness is the number of pixels against the printed size: 3307 pixels across print 28 cm wide at 300 DPI whatever the file says. The checker shows the file’s value apart, and works out the real resolution from the print width you enter.

### Can I print a JPEG as a DTF transfer?

Not as it is: JPEG cannot be transparent, so whatever surrounds the design, usually white, prints with it as a box of ink. Remove the background in an image editor and save a PNG with transparency.

### Is my image uploaded anywhere?

No. The page reads the image in your browser, in the background so the page stays responsive, and shows what it found; nothing is sent to printblob.com or anyone else.

### What can the checker not see?

Lines and text too thin to transfer, which depend on your printer’s minimum, commonly 0.5 to 1 mm; the colour mode your printer asks for; and whether a white area inside the design is meant to print white. The DTF print file requirements guide explains how to check those by eye.

## Print files that pass, from your own shop

In a WooCommerce shop with [PrintBlob](/), customers design on the product page, and [PrintBlob Pro](/docs/pro/) makes each printed side a transparent PNG at 300 DPI at the print area’s exact size when the design is added to the cart, ready for a gang sheet; while customers place an image, the designer warns below 150 DPI. What a DTF file needs, point by point, is in [DTF print file requirements](/guides/dtf-print-file-requirements/); to see how large an image prints sharp, use the [image print size calculator](/tools/print-size/).

## Sources

- Inkthreadable Help Centre, [Gradients & transparency](https://help.inkthreadable.co.uk/en/articles/435627-gradients-transparency) (23 January 2026, read 27 October 2026): “Pixels that are either 0% or 100% transparent are perfect”; semi-transparent pixels print unpredictably by DTG, DTF and sublimation.
- Transfer Superstars, [How to remove backgrounds from images for DTF transfers](https://www.transfersuperstars.com/blogs/transfer-superstar-exclusives/how-to-remove-backgrounds-from-images-for-dtf-transfers-a-complete-guide) (10 October 2025, read 27 October 2026): background removal that leaves semi-transparent pixels “creates white outlines around your design when transferred”.

## Get PrintBlob Pro

Pro adds print-ready files, back printing, a 3D view and a production print queue to the free designer. Paid with Stripe in US dollars, no tax added; one domain per licence.

- **$69 a year**: [Buy the yearly licence](https://printblob.com/pricing/#buy). Full refund within 14 days.
- Limited-time offer until 31 December 2026: **$99 once**: [Buy the lifetime licence](https://printblob.com/pricing/#buy). Full refund within 14 days.

## Try it on your own shop

PrintBlob is free in the WordPress.org plugin directory: install it, turn the designer on for a product and take a design order. PrintBlob Pro is $69 a year or $99 once (limited-time offer until 31 December 2026), with a full refund within 14 days.

[Install PrintBlob free](https://wordpress.org/plugins/printblob/) · [Download free (0.8 MB)](https://printblob.com/downloads/printblob.zip) · [Free and Pro compared](https://printblob.com/pricing/)

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Page: https://printblob.com/tools/dtf-image-checker/

See also: [docs](https://printblob.com/docs/index.md), [guides](https://printblob.com/guides/index.md), [features](https://printblob.com/features/index.md), [situations](https://printblob.com/situations/index.md), [compare](https://printblob.com/compare/index.md), [demos](https://printblob.com/demos/index.md), [themes](https://printblob.com/themes/index.md).