or click this area to pick one or more PNG files
This is the single most common mix-up. Web pages and most image viewers are white to begin with, so a white-backed image blends into them completely and looks like the background was already removed. The white rectangle only shows up once you place it on a dark poster, a coloured slide or another photo. Which means you cannot judge transparency by looking at it on white: you have to put the image on a background that clearly contrasts with it, or count the alpha value of the pixels directly. This page does both.
Renaming a JPG to .png is the bluntest one: the extension changed, but the file is still a JPG inside, there is no alpha channel at all, and the background is solid white. Picking the wrong export format after cutting out a subject does the same thing — save as JPG once and the transparent areas are filled with white, which converting back to PNG will not recover. A third case is a sloppy cut-out: a ring of semi-transparent white or grey is left around the subject, which looks fine on its own but turns into an obvious outline against a dark background.
Every pixel in a PNG carries an alpha value alongside its colour: 0 is fully transparent, 255 is fully opaque, and everything between is semi-transparent. Fully transparent pixels are what cuts the background out. Semi-transparent pixels usually sit along the subject's edges, in shadows and in glass-like surfaces — they make edges look smooth, but they also let a little of whatever is underneath show through. This page counts the two kinds separately precisely so you can tell "the background really is empty" apart from "the edges just fade out".
A logo laid over a photo or a coloured block, a product shot that needs a new background, an icon dropped into a slide, artwork that will be overprinted — all of these need real transparency, or you get a white rectangle. Conversely, if the image will only ever appear on a white page, a white-backed JPG is usually smaller. Once you have confirmed the background really is transparent, you can adjust the composition with Online Image Cropper — cropping does not damage the alpha channel.
Every pixel in a PNG can carry alpha (transparency) information. This tool reads the pixel data and counts the fully transparent, partially transparent and fully opaque pixels, which tells you whether the PNG genuinely has a transparent background or soft translucent edges.
Some images only appear to have a transparent background: it has in fact been filled with white, grey or a painted-on checkerboard pattern, and the alpha value of those pixels is still 255 — fully opaque. Because this tool judges transparency from the actual alpha values rather than from how the image looks, it can tell “really transparent” apart from “looks transparent”.
A fully transparent pixel has an alpha of 0 and hides nothing behind it. A translucent pixel has an alpha between 1 and 254 and blends with whatever is underneath. Icons, logos and cut-out edges commonly use translucent pixels to keep their outlines smooth.
A transparent image can reveal different flaws on white, black, red, green or blue. A white fringe, for instance, is invisible on a white background but glaringly obvious on a dark one. Previewing against several backgrounds helps you spot ragged cut-out edges, leftover background colour and translucent areas.
No. The transparency check only reads the image and renders a preview; it never rewrites, compresses or exports anything. Your original file is left untouched, and the preview disappears once you reload or clear the page.
No. Images are read and analysed entirely inside your browser and never leave your device — which makes this safe for design drafts, unreleased logos, product shots, screenshots and any other PNG you would rather not send anywhere.
This tool is built for checking PNG transparency and accepts PNG files only. JPG has no alpha channel at all, and WebP and SVG handle transparency differently — convert those to PNG first if you need to check them here.