Transparent PNG checker
Is the background really transparent? Find faint leftovers and stray specks, and clean them.
or drop one here. It stays on your device: nothing is uploaded.
How to check if a PNG is transparent
Drop the file in the box above. In a second it says whether the background is transparent, how much of the picture is see-through, and where pixels are hiding that you cannot see. With “Checker” chosen under the picture, the checkerboard is the transparent part; anything you see on it is something that will print.
Without a tool, open the file in any editor that shows a checkerboard behind see-through areas. If the corners show white instead, the background is solid. That catches the obvious case, but not the faint leftovers below, which is why the check here also looks at every pixel.
What this checks
- Whether the background is transparent at all. A file with no transparency prints as a full rectangle, background and all.
- Nearly invisible pixels. Anything under 10% solid cannot be seen on a screen, yet a printer still prints it.
- Small stray pieces. Dots and crumbs standing apart from the design, the usual leftovers of an automatic background eraser.
- Soft edges. How much of the picture is half-transparent. A little is normal (it is what makes edges smooth); a lot on a dark shirt can print as a pale fringe, and the checker can make those edges hard.
Why a clean screen is not a clean print
On a screen a pixel that is 3% solid looks like nothing. A direct-to-garment printer sees a pixel with something in it. On a dark shirt it first lays down white ink wherever the file is not empty, then the color on top. A cloud of 3% pixels becomes a cloud of thin white ink: the haze, the dots and the ghost of the old background that people find on their first sample.
Looking at the design on black, white and a strong color shows most of it. The switch under the picture does that, and the highlight shows where the pixels are that you cannot see at all.
Fixing what it finds
- 1No transparencyCut the design out with the background remover, then check the result here.
- 2Nearly invisible pixelsPress “Clean this file”. They are made fully transparent; nothing you can see changes.
- 3Stray piecesLook at where the orange marks are. If they are crumbs, tick the box to remove them too. If they are part of the design, leave them.
- 4A pale rim on blackTick “Make the edges hard” and move the slider while you watch the preview on black. For a design cut out of a white background, also tick “Remove a white fringe”. Then press “Clean this file”.
The cleaned PNG keeps the pixel size of the picture that was checked. Nothing is uploaded: the file is read by your browser.
Read more on the blog
- How to Fix White Halos Around Transparent PNGs on Dark Hoodies
- Best DPI and Upscaling Settings for Midjourney and AI T-Shirt Prints
Questions people ask
How do I check that an image has a transparent background?
Drop it into the checker on this page. It says at once whether the background is transparent, and marks the faint pixels and stray specks a quick look misses. In an image editor, a transparent background shows as a gray and white checkerboard; a JPG never has one.
Why did my design print with a white box around it?
The file had no transparent background: the white around the design is made of real pixels, and a garment printer prints every pixel it is given. Save the design as a PNG with the background removed, and check it here before you send it.
What are stray pixels, and why do they matter?
Background erasers often leave pixels behind that are almost, but not fully, transparent. On a screen they are invisible. On a dark shirt the printer lays white ink under them, and they show up as a faint haze or as dots around the design.
How do I fix a white halo around a PNG?
A halo comes from the edge pixels: half see-through, and often still mixed with the white the design was cut from. Check the file here, tick Make the edges hard and move the slider until the edge looks clean on the black preview. For a design cut out of white, tick Remove a white fringe too, then download the clean PNG.
Is my image uploaded anywhere?
No. The file is opened and checked in your browser, on your own device. Nothing is sent to SlapMake or to anyone else.
Does a JPG have a transparent background?
No. The JPG format cannot store transparency, so every JPG prints as a full rectangle. Use PNG for print files that need a see-through background.
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