By BGNinja Team · Last updated: July 2026
Everyone asks for "a PNG with a transparent background": few people can say what that actually is, why a JPG can't do it, or why hair is the part that always goes wrong. Here's the whole story in plain language.
A digital photo is a grid of pixels, and each pixel normally stores three numbers: how much red, green and blue light it shows. Mix them and you get any colour on screen. A transparent image adds a fourth number (the alpha channel) that says how opaque the pixel is, usually from 0 (fully invisible) to 255 (fully solid).
That single extra number is the entire trick. When a browser, design app or slide deck draws the image, it blends every pixel with whatever sits behind it, in proportion to its alpha value. A pixel at alpha 0 vanishes completely; a pixel at alpha 128 shows half itself and half the background behind it. The famous grey-and-white checkerboard you see in editors isn't part of the image at all: it's just how software visualises "nothing here".
That in-between range matters more than most people realise. Real objects don't end in a hard line: hair, fur, glass, smoke and soft shadows all fade out gradually. Partial alpha values are what make a cutout look like a photograph instead of a sticker cut with scissors.
Not every image format can store that fourth number, and this is where most confusion starts.
| Format | Transparency | Compression | Best for |
|---|---|---|---|
| PNG | Yes, full 8-bit alpha | Lossless (larger files) | Cutouts, logos, graphics, anything layered |
| JPG | No, none at all | Lossy (small files) | Finished photos with a background |
| WebP | Yes, full alpha | Lossy or lossless, smaller than PNG | Web images where file size matters |
JPG simply has no alpha channel. The format was designed in the early nineties to compress photographs, and photographs fill the whole frame. If you save a cutout as JPG, the transparency is silently flattened onto a solid background (usually white) and it's gone for good. This is why a "transparent JPG" someone sends you always arrives with a white box around the logo.
PNG is the safe default. It stores alpha losslessly, every tool ever made accepts it, and marketplaces, print shops and design apps all expect it. The price is file size: a detailed photo cutout as PNG can be several times larger than the same image as JPG.
WebP is the modern middle ground. It supports full transparency and typically compresses 25–35% smaller than PNG, which is why websites love it. Its only weakness is compatibility outside the browser: some older design tools, embroidery/print services and upload forms still reject it. Rule of thumb: use WebP on your own website, send PNG to everyone else.
Cutting out a coffee mug is easy: the edge is a clean curve, and each pixel is clearly mug or clearly background. Hair is a different sport. A single strand is often thinner than one pixel, so the pixel it passes through is a blend: maybe 30% hair, 70% background. There is no correct "keep or delete" answer for that pixel; the only honest answer is partial alpha.
Good background removal therefore has to solve two problems at once. First, estimate the right opacity for every edge pixel: that's what turns a jagged paper-doll outline into soft, believable hair. Second, remove the old background's colour from those blended pixels. A pixel that was 30% blonde hair and 70% blue sky still contains blue; if the blue isn't subtracted, the cutout carries a ghostly halo of the old background onto the new one. That fringe is the tell-tale sign of a cheap cutout.
This is exactly where segmentation models earn their keep: they've seen millions of examples of hair, fur and soft edges, and learned to predict sensible alpha values instead of a binary keep/delete mask. It's also why results are best when hair contrasts with the background: more on that in our guide to shooting photos that cut out perfectly.
Drop any photo into BGNinja and download the cutout in seconds: free, no account, nothing kept.
Make a transparent PNG →A PNG whose pixels carry an alpha (opacity) value in addition to colour. Wherever alpha is zero, the background behind the image shows through.
No, JPEG has no alpha channel. Saving a cutout as JPG flattens it onto a solid background permanently. Use PNG or WebP instead.
WebP is smaller and great for your own website; PNG is universally accepted. When a platform asks for a transparent image without specifying a format, PNG is always the safe answer.
The edge pixels still contain colour from the old background. A good cutout removes that tint; if a patch survives, BGNinja's erase brush lets you paint it away.