Guide
Why your transparent PNG looks like it has a white background
This is the most common complaint about cutouts anywhere, and nine times out of ten the file is perfect. The failure is happening in the next application along, and once you know what it is doing it takes ten seconds to prove.
What a PNG is actually storing
Every pixel in a transparent PNG carries four numbers. Three describe a colour and the fourth describes how much of that pixel exists. A pixel with a fourth number of nought is not white, not black and not invisible-but-present: it is a hole, and the file says nothing whatsoever about what should appear there.
Which means the file, on its own, cannot look like anything. Something has to decide what goes behind the hole before a single pixel can be drawn, and that decision belongs to whatever is displaying it. Different programs make it differently, and they are all behaving correctly.
| Program | What it puts behind the holes |
|---|---|
| A browser tab | the page — usually white, unless the page is not |
| An image viewer | a grey checkerboard, on purpose, so you can see the holes |
| A word processor | the paper |
| Presentation software | the slide, which may be any colour |
| A photo editor | a checkerboard, and a layer if you add one |
The ten-second test
Put the file somewhere that is definitely not white. A coloured slide is ideal; a coloured cell in a spreadsheet will do. If the subject sits on the colour with nothing around it, the cutout is correct and the problem lives in whichever program showed you white. If a rectangle of white arrives with it, the ground really is in the file, and you need to cut it out rather than argue with the viewer.
Three things that genuinely destroy the channel
Saving as JPG. JPEG has no fourth channel in its specification. Anything see-through is composited against something — usually white, occasionally black — at the moment of saving, and there is no undo. This is permanent and it is the most common way a good cutout is lost.
Passing through a chat app. Most of them re-encode images on send to save bandwidth, and re-encoding usually means JPG. Send the file as a document or attachment instead of as a photo.
Pasting rather than inserting. A copy taken from a viewer often carries the composited picture rather than the file, so the paste arrives flattened against whatever that viewer was using. Insert the file from disk instead.
When the file really is wrong
There is one case where the complaint is accurate, and it has a distinctive look: a thin pale line following the subject exactly, a pixel or two wide, visible only on a dark ground. That is not a background — it is the boundary pixels keeping some of the light that was behind them. Nothing downstream caused it and nothing downstream will fix it.
On this site the fix is either a narrower band, which discards those pixels along with anything delicate, or the take-away brush at step 3 with a soft edge, run once around the outline. Check the result on the near-black backing swatch rather than the checkerboard, because a pale halo is close to invisible on light grey squares.
Questions that follow from this
- How do I check the file itself rather than what an app is showing me?
- Drag it onto a browser tab. A browser composites a PNG against the page, and an empty tab is white, so that test alone proves little — but zoom to the edge and look for a checkerboard in an image viewer, or drop the file onto a coloured slide. If the subject sits on the colour with no rectangle around it, the alpha channel is intact and every other explanation is about software downstream.
- It looked right in the editor and wrong after I sent it.
- Then something in the sending flattened it. Chat apps re-encode almost everything that passes through them, usually to JPG, which has no alpha channel; email clients frequently do the same to keep attachments small. Attaching the file as a document rather than as an image is the usual way around it.
- Word put my logo in a white box.
- Word keeps the alpha channel in a PNG but a great many logos are not actually transparent — they are white artwork exported on a white rectangle, which is indistinguishable from transparency until the moment it lands on a coloured page. Open the file somewhere that shows a checkerboard. If there is no checkerboard behind the mark, the box is in the file and the fix is to cut it out.
Read next
- Make a picture transparentThe same four steps, with the file-format question answered on the way out.
- Hair, fur and every other soft edgeWhat the uncertain band is, what widening it costs, and the edges nobody wins.
- Cut the subject outOpen a photo with a clearly separable subject, let colour and contrast propose the edge, correct it by hand, save a transparent PNG.
- Cut out hair and furA wider uncertain band and a softer ramp, set that way before you arrive.