PNG Transparency Checker
Drop in an image and find out whether it has a real transparent alpha channel — and whether any pixels in it are actually transparent. Two different questions, both answered here.
Your file never leaves your device. Everything runs in your own browser — there is no upload, no server and nothing stored.
- File name
- File type
- File size
- Dimensions
- Alpha channel present
- Fully transparent pixels
- Semi-transparent pixels
Why a transparent PNG and a white background look identical
On a white page they are the same picture. The difference only appears when something else is behind the image — a coloured background, a dark garment, another layer. At that point a file with no transparency shows a white rectangle around the artwork, and a file with real transparency does not.
That is why this check is worth doing before you commit a design to print rather than after.
What the results mean
Alpha channel present tells you whether the format is even capable of transparency. Fully transparent pixels tells you whether it is actually being used. You need both to be true for the file to behave as clipart.
Semi-transparent pixels are partly see-through. A healthy cut-out has plenty of them along its outline — they are what makes a curve look smooth instead of stepped. A file with zero semi-transparent pixels but many fully transparent ones has usually been cut with a hard threshold, and its edges will look jagged when enlarged.
Checking the edges, not just the background
A file can pass this test and still print badly. When artwork is cut from a white background, the edge pixels sometimes keep a trace of that white, which appears as a pale halo once the design is printed on something dark.
Use the On black toggle above and look closely at a curved edge. Clean artwork fades into its own colour. Artwork with a halo has a light rim that becomes more obvious the closer you look.
Related
- How to check if a PNG is really transparent — the longer version of this, including what to do when a file fails.
- PNG Resizer — resize a file without losing its transparency.
- Cutlark collections — every bundle is supplied as individual transparent PNGs, and every product page shows the artwork on black so you can judge the edges before buying.
Common questions
Does my image get uploaded anywhere?
No. The file is read by your own browser using the FileReader and Canvas APIs, examined on your device, and discarded when you close or reload the page. It is never sent to Cutlark or to any other server.
What is the difference between having an alpha channel and being transparent?
An alpha channel is the capability; transparency is whether it is actually used. A file can have an alpha channel where every pixel is set to fully opaque, which behaves exactly like a flat image. This tool reports both separately, because only the second one matters in practice.
Why does it say my JPG has no transparency?
The JPG format has no alpha channel at all, so a JPG can never be transparent. Saving a JPG as a PNG does not restore a background that was already discarded.
What counts as a semi-transparent pixel?
Any pixel with an alpha value between 1 and 254 — partly see-through rather than fully solid or fully invisible. These are normal and desirable: they are what makes an edge look smooth instead of jagged.
What file types can I check?
Anything your browser can display as an image: PNG, WebP, AVIF, GIF, JPG, BMP and SVG. PNG and WebP are the formats where the answer is usually in question.