PNG transparency basics: why JPG fills it in and how to keep it
A logo's background turns white, or you want to keep it transparent but smaller — here is how PNG transparency (the alpha channel) works, why converting to JPG loses it, and how WebP keeps transparency while shrinking the file.
Transparency means there is no background
PNG stores not just a color per pixel but also an opacity (the alpha channel). That alpha is what lets you have cut-out images with no background, or a logo whose rounded corners and shadows blend naturally onto whatever is behind them.
The checkerboard pattern you see behind a logo in an image editor is the program's way of saying 'this area is transparent' — it is not a white fill. Transparency is the absence of a background, not a color, which makes the rest of this easier to follow.
Why JPG turns the background white
JPG cannot store opacity. So when you convert a transparent PNG to JPG, the transparent areas get filled with white (or black, depending on the tool). 'I saved my logo as JPG and it got a white box around it' is almost always this.
Once that fill is baked in, you cannot turn it back into transparency. Keep images that need transparency as PNG (or WebP) for editing and storage, and only convert to JPG for final uses where transparency does not matter.
Formats that keep transparency: PNG and WebP
The main formats that preserve opacity are PNG and WebP. PNG is highly compatible and opens almost anywhere, but gets heavy for photo-like images. WebP supports transparency too and saves much smaller than PNG, which makes it great for the web.
Keep PNG as your master and export WebP for the site, and you keep transparency while gaining speed. Only fall back to PNG when the recipient's environment is old enough not to support WebP.
Making a transparent PNG smaller
To shrink a file while keeping transparency, try WebP first — it preserves alpha and can cut a photo-heavy PNG to a fraction of its size. For icons and logos with few colors, simply compressing the PNG is often enough.
Our PNG to WebP and PNG compress tools both run in the browser, so you keep the transparency and shrink the file without sending it to any server.
If you do not need transparency, go JPG
If the image already has a full photographic background, or you never use the transparent areas, converting to JPG keeps the file small and easy to handle. Holding a non-transparent photo as PNG just wastes space.
Decide up front: does this image need a see-through background? If yes, PNG or WebP; if no and you want it light, JPG. That one question settles most format choices.
Bottom line: PNG/WebP for transparency, JPG if not
Transparency is the absence of a background and cannot be saved in JPG. Keep logos, icons, and cut-outs in PNG or WebP, and reach for WebP conversion or compression when you need them smaller.
PNG ⇄ JPG conversion, PNG → WebP, and PNG compression are all free, signup-free, and in-browser on Filewisp.