PNG files: lossless, transparent, and often larger than you expect

Why PNG is exact, when it beats JPG, and why a photograph saved as PNG is enormous. Convert PNG in your browser, no upload.

At a glance

Type: Image
Compression: Lossless
Extensions: .png
MIME type: image/png
Also known as: Portable Network Graphics

PNG was designed in 1996 for a specific reason: GIF used LZW compression, LZW was patented, and the web needed a free replacement. What came out of that effort was better than the thing it replaced in every dimension — 24-bit colour instead of 256, a real alpha channel instead of one transparent index, and DEFLATE compression that is genuinely lossless. Decode a PNG and you get back exactly the pixels that went in, every time.

Lossless is the whole story, and it cuts both ways. PNG is the correct format for screenshots, diagrams, line art, logos and anything with text, because it reproduces sharp edges exactly where JPEG leaves a soft haze around them. It is the wrong format for photographs, because losslessly describing an image where no two adjacent pixels match takes an enormous number of bytes. A photo that is 800 KB as a JPG can be 5 MB as a PNG and look no better.

The alpha channel is the other reason PNG persists. Eight bits of transparency per pixel means genuine soft edges — antialiased text, drop shadows, a logo that can sit on any background. That capability is why PNG remains the interchange format for design work even though WebP now compresses the same pixels considerably better.

Two details worth knowing. A PNG can be palette-based (up to 256 colours, like a GIF) or full colour, and a palette PNG of flat graphics can be dramatically smaller — which is why some optimisers shrink files without any visible change. And PNG holds exactly one image: animation lives in the separate APNG extension, which most tools do not write, so an animated GIF converted to PNG here yields its first frame only.

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FAQ

Is PNG really lossless?

Yes, literally. Decoding a PNG returns exactly the pixels that were encoded. It compresses by finding redundancy, the way ZIP does with a document, rather than by discarding detail.

Why is my PNG so much larger than the JPG?

Because it stores real information about every pixel. Photographs have no two identical neighbours and compress badly under lossless rules, while JPG got its small size precisely by throwing detail away.

When should I use PNG instead of JPG?

Screenshots, text, diagrams, line art, logos, and anything needing transparency. Also before editing, when you plan to save repeatedly — PNG does not accumulate damage the way JPG does.

Does converting a JPG to PNG improve it?

No. It stops further loss but cannot undo what the JPG already discarded. Those artefacts become part of the image and PNG preserves them faithfully.

Does PNG support animation?

Only through the separate APNG extension, which most tools do not produce. A PNG holds one image, so converting an animated GIF here gives you its first frame.

PNG or WebP?

WebP compresses the same pixels considerably better and also supports transparency, so it is the better choice for the web. PNG remains the safer interchange format for design tools and anything that has to open everywhere.

Why would I convert a PNG to BMP?

Only when software demands it — some older Windows tools, scientific instruments and microcontroller code read raw pixels and nothing else. BMP is uncompressed, so the file gets much larger and transparency is lost.

Can I make a favicon from a PNG here?

Yes, with one caveat: the output is PNG data in a file named .ico. Browsers accept that as a favicon, but it is not a true multi-resolution ICO and will not serve as a Windows application icon.