What Is PNG? The Lossless Graphics Format

PNG (Portable Network Graphics) is a lossless raster image format: it stores a grid of pixels and preserves every one of them exactly, with no quality thrown away. Its two defining traits are that losslessness and a true transparency channel, which together make it the standard format for logos, screenshots, icons, and any graphic that needs a see-through background.

PNG appeared in the mid-1990s as a free, patent-unencumbered replacement for GIF, after the compression method inside GIF turned out to be patented and its owner began asking for royalties. The people who designed PNG deliberately built it on DEFLATE - the same open compression algorithm used inside ZIP and gzip files - so anyone could read or write a PNG without a licence. That decision is why PNG is everywhere on the web today and GIF has faded to little more than animation.

What is inside a PNG file

A PNG is a bitmap: a rectangular grid of pixels, each with its own colour, exactly the kind of image a photo or screenshot is (as opposed to the shape-based instructions of a vector file - that split is covered in raster vs vector). What makes PNG different from JPG is how it packs that grid down. It applies DEFLATE compression, which finds and shortens repeated patterns without altering a single pixel, so decompressing a PNG gives back the original bit-for-bit. That is what lossless compression means, and it is why a PNG never develops the blocky fringes that repeated JPG saves produce.

PNG can store an image in three ways. Truecolor holds full 24-bit RGB, or 32-bit when an alpha channel is added; grayscale drops the colour for images that do not need it; and indexed colour - sometimes called PNG-8 - restricts the image to a palette of up to 256 chosen colours, which keeps small flat graphics tiny. All of them are RGB or gray, never CMYK, so PNG is a screen and web format rather than a print-separation one.

Transparency is what sets PNG apart

PNG's headline feature is a proper alpha channel. Instead of GIF's single on-or-off transparency, where a pixel is either fully visible or fully gone, PNG stores 256 levels of transparency per pixel - so an edge can fade smoothly from solid to invisible. That is why a PNG logo sits cleanly on any coloured background without a jagged white halo, and why app icons and UI elements are almost always PNGs. The mechanics of that channel are the subject of alpha transparency; the practical upshot is that if an image needs to be see-through, PNG is usually the answer. The newer WebP format also supports transparency at smaller sizes, and PNG vs WebP weighs that trade-off.

What PNG is good for

PNG is the right choice whenever an image has sharp edges, flat areas of colour, crisp text, or transparency: logos, icons, screenshots, diagrams, charts, line art, and any graphic layered over something else. Because it is lossless, it is also the safe format to edit and re-save repeatedly - each save is a perfect copy, so the quality erosion known as generation loss never sets in the way it does with JPG. Designers keep working files as PNG for exactly that reason.

Where PNG is the wrong choice

PNG struggles with one thing: ordinary photographs. A photo is millions of subtly varying pixels with few repeating patterns, so DEFLATE finds little to shorten, and a lossless PNG of a photo ends up several times larger than the same shot as a JPG - which is why so many upload forms, email limits, and marketplaces reject heavy PNGs. When your PNG is a photo and the size is the problem, convert it: PNG to JPG re-encodes it as a far smaller JPG, flattening any transparent areas onto a white background and letting you set the quality with a slider. To keep the file as a PNG but bring the weight down for upload, Compress PNG shrinks it instead. The reverse trip - JPG to PNG - gives you a lossless PNG copy of a JPG, though it cannot restore detail the JPG already discarded; it only stops any further loss from that point on. Both conversions run entirely in your browser, so the image is never uploaded. For how PNG lines up against every other format, the image formats field guide lays them side by side.

FAQ

Is PNG lossless? Yes, always. PNG compression preserves every pixel exactly, so a PNG never loses quality when it is saved or re-saved. The trade-off is file size: for photographs, that fidelity makes PNG much larger than a lossy JPG.

Does PNG support transparency? Yes - a full alpha channel with 256 levels, so pixels can be partly transparent and edges fade smoothly. This is PNG's main advantage over JPG, which has no transparency at all.

Is PNG better than JPG? Neither is better outright; they are built for different images. PNG wins for logos, screenshots, text, and anything needing transparency. JPG wins for photographs, where it produces far smaller files. JPG vs PNG covers the full choice.

Why is my PNG file so large? Almost always because it is a photograph. PNG keeps every pixel, and photos have little repetition for its compression to exploit, so the file stays big. Saving that photo as a JPG, or running it through PNG to JPG, will cut the size dramatically.

Can a PNG be animated? Not in its standard form - a PNG is a single still image. There is a later extension called APNG that adds animation, but it is not part of the original format and is not what most software means by "PNG".