What Is a PNG File? The Format for Sharp Graphics and Transparency

Lossless compression: every pixel preserved

PNG uses lossless compression, which means it shrinks the file without discarding any image data at all — every pixel is stored exactly, and the image can be opened, edited and re-saved endlessly with zero degradation. This is the opposite of JPG's lossy approach, and it is exactly what you want for a screenshot of text, a logo with crisp edges, or a chart with fine lines: no smudging, no halos, no artifacts around the sharp bits.

The trade-off is size. For a photograph — millions of subtly different colours — lossless storage produces a much larger file than JPG would, with no visible benefit. So while PNG is unbeatable for graphics, it is the wrong choice for photos, where its files can be five or ten times larger than an equivalent JPG that looks the same.

Transparency: PNG's standout feature

PNG's most useful trick is the alpha channel: it can store transparency, so parts of the image can be fully or partially see-through. This is why logos, icons and cut-out subjects are almost always PNGs — a logo saved as PNG sits cleanly on any coloured background, while the same logo as JPG arrives stuck on an ugly white rectangle. The transparency is per-pixel and can be partial, giving smooth, anti-aliased edges rather than a jagged cut-out.

This makes PNG the natural output for background-removal tools and the standard format for any graphic that needs to be layered onto other content in a design, a slide or a web page. When someone asks for a logo "with a transparent background", they are asking for a PNG.

PNG-8 vs PNG-24, and where PNG falls short

There are two common flavours. PNG-8 uses a palette of up to 256 colours and produces very small files — ideal for simple icons and flat graphics. PNG-24 (and 32, with transparency) stores full colour, handling millions of shades for richer graphics and smooth gradients at a larger size. Most tools pick the right one automatically, but knowing the distinction explains why one PNG is tiny and another is huge.

PNG has no animation (that is what APNG, GIF or video are for) and, being lossless, is simply too heavy for photographs meant for the web. For photos, JPG, WebP or AVIF will always be smaller. Think of PNG as the format for graphics and transparency, not for photographic content.

How to open, convert and compress a PNG

Every browser, phone and computer opens PNG natively. To shrink one — PNGs of complex graphics can still get large — an image compressor can reduce the palette or apply lossless optimisation, and resizing to the display dimensions helps most of all. To turn a PNG into a JPG (to shrink a photo-like image, accepting the loss of transparency) or a JPG, HEIC or WebP into a PNG (to gain lossless quality or transparency), use an image converter. Note that converting a JPG to PNG will not restore detail JPG already discarded — it just stops further loss. OfficePad runs all of this in your browser.

Frequently asked questions