What is a PNG file? What it’s for, how to open one, and when to use JPG instead

The short version

• It’s a picture format that loses nothing. “Lossless” means a PNG comes back exactly as it was saved, pixel for pixel.
• It can be see-through. That’s why logos and icons are usually PNGs: they sit on any background without a white box round them.
• It’s the wrong choice for photos. Our 60 photos were 49 MB as PNGs and 3.6 MB as JPGs.
• You can already open one. Every main web browser opens PNG files, and so do Paint on Windows and Preview on a Mac.
• Converting to JPG is free. In Paint, choose JPEG when you save; in Preview, choose File > Export.
• Google takes it. Google Search, Merchant Center and Business Profile all accept PNG.

What is a PNG file?

PNG stands for Portable Network Graphics. The format is defined by a standard published by W3C, the body behind the web’s own standards, and the PNG specification describes it as “an extensible file format for the lossless, portable, well-compressed storage of static and animated raster images.”

In plain words: lossless means nothing is thrown away when the picture is saved, so it opens exactly as it went in. Raster means it’s a grid of coloured dots (pixels), like a photograph, rather than shapes drawn from instructions, like an SVG logo. The specification also says PNG “provides a patent-free replacement for GIF”, the older format it replaces.

Two features matter for a business:

• Transparency. The specification lists “an optional alpha channel”, which is its term for see-through pixels. Each pixel can be solid, fully transparent, or somewhere in between, so a logo can sit on a coloured page or a photo without a box round it.
• Animation, officially, since 2025. The current version, the third edition, became a W3C Recommendation on 24 June 2025 and covers “static and animated” images. Some guides still say PNG can’t do animation. That’s out of date.

What a PNG file is used for, and what it isn’t

Mozilla’s guide for web developers, the image file type and format guide, puts it in one line: “PNG is preferred over JPEG for more precise reproduction of source images, or when transparency is needed.” In practice that means:

• Logos and icons, especially anything that has to sit on a coloured background.
• Screenshots of software, websites and documents, where the text has to stay crisp.
• Diagrams, charts and illustrations with flat colours and sharp edges.
• Any image that needs a see-through background.

Photographs are the exception. A photo has millions of slightly different colours, and keeping every one of them exactly makes the file big. JPG throws away detail the eye doesn’t miss, which is why the same photo is usually far smaller as a JPG.

One of the guides on Google’s first page for this question says PNG files “are smaller than JPEGs, meaning they take up less space and download faster”, and that they “do not support animation”. For photographs, our own files say the opposite on size, and the standard itself has covered animation since 2025.

What we found converting our own images

Every post on this blog has a share image: the picture that appears when someone posts the link. Until this month the older ones were all PNGs. We’ve converted them to JPG (three are waiting for another test to finish) and measured the files. The full test is in our post on JPG or PNG for your website; here are the numbers.

The images with words on them came out about 82% smaller rather than 93%. Lettering is where JPG needs care, so we saved those with full colour detail to keep the edges of the letters clean. And the one test that went the other way is the one you’d expect: our logo as a JPG was almost twice the size of the PNG, and its transparent background turned black.

How to open a PNG file

You almost certainly have something that opens it already. Every main web browser does: Mozilla’s guide lists PNG support as “Chrome, Edge, Firefox, IE, Opera, Safari”, so dragging the file into a browser window always works.

• On Windows: Paint opens and saves PNG files. Microsoft’s Paint page says you can save “in various file formats, including PNG, JPEG, BMP and GIF, among others.”
• On a Mac: Preview opens it. Apple’s guide to converting files in Preview lists PNG among the formats it handles.

How to convert a PNG to JPG for free

• Windows, in Paint: open the PNG, choose Save as, and pick JPEG. Microsoft’s page: “Paint allows you to choose the format when you save your image.”
• Mac, in Preview: Apple’s steps are to open the file, “then choose File > Export”, and pick JPEG from the Format menu.

Two warnings. First, don’t convert anything with a see-through background, such as a logo: JPG has no transparency, so the clear parts get filled in. Ours went black. Second, don’t just rename the file from .png to .jpg; that changes the name, not the format. Google’s image guidance says “It's also a good idea to have the extension of your filename match with the file type.”

PNG or PDF?

They’re different kinds of file. A PNG is one picture. A PDF is a document: it can hold pages of text, pictures and layout, and it prints the same everywhere. If you have a logo, a screenshot or a diagram for a website, use PNG. If you’re sending something someone will read, sign or print, use PDF. Preview on a Mac can save in either: Apple’s Format list includes both PDF and PNG.

Does Google accept PNG files?

Yes, everywhere a small business is likely to need it:

• Google Search: “Google Search supports images referenced in the src attribute of img in the following file formats: BMP, GIF, JPEG, PNG, WebP, SVG, and AVIF.”
• Google Merchant Center: its image link rules list “PNG (.png)” among the supported file formats.
• Google Business Profile: the photo guidelines say “Format: JPG or PNG”, with a size “Between 10 KB and 5 MB.”
• eBay, for comparison: its picture help page accepts “JPEG, PNG, GIF, TIFF, BMP, WEBP, HEIC, or AVIF”, up to 12MB a file.

The size limits are where PNG photos get caught out. A large photo saved as a PNG can easily go over Business Profile’s 5 MB, where the same picture as a JPG would fit comfortably.

What argues the other way

• Lossless matters while you’re still editing. Each time a JPG is saved again, it can lose a little more detail. If you’ll edit a picture several times, keep the working copy as a PNG and make the JPG at the end.
• Newer formats can beat both. Mozilla’s guide adds: “WebP/AVIF provide even better compression and reproduction, but browser support is more limited.” Our posts on WebP and AVIF have our own numbers, and the places that still won’t take them.
• Our test is small and particular. Our photos were generated by AI and are smooth, clean images; busy, grainy photos can behave differently. The direction of the result is common knowledge; the exact percentages are ours.

Sources, and what we checked

• W3C, Portable Network Graphics (PNG) Specification (Third Edition), W3C Recommendation 24 June 2025: the definition, the GIF replacement, the alpha channel and animated images.
• Mozilla, Image file type and format guide: when to prefer PNG, browser support, and WebP and AVIF.
• Google, Image SEO best practices: the formats Google Search supports and file extensions.
• Google, Image link [image_link] (Merchant Center) and Manage your Business Profile photos and videos.
• eBay, Adding pictures to your listings.
• Microsoft, Draw, Create and Edit with Paint; Apple, Convert image file types using Preview on Mac.
• All of the pages above were read on 28 October 2026, and again on 30 October 2026, the morning we published.
• Our test: 60 share images from this blog (1,200 × 630 pixels, photographs) converted on 3 October 2026, and 114 older share images converted and published on 28 October 2026, all as JPG at quality 85; details in our JPG or PNG post.