What a PNG file is
What a .PNG file is, what it does well, what opens one, and how to convert it — with every conversion running in your own browser.
What a PNG file is
A PNG is a bitmap image stored without losing anything. Every pixel you put in comes back exactly as it went in, however many times the file is opened, edited, and saved again. That is the whole promise of the format, and it is why a PNG of a screenshot stays crisp where a JPG of the same screenshot grows fuzzy around the text.
The cost is size. PNG compresses by finding repetition — runs of identical pixels, rows that resemble the row above — which works extremely well on flat colour and poorly on a photograph, where almost no two adjacent pixels are the same. A screenshot might be a tenth the size as a PNG than as an uncompressed bitmap; a photograph is often several times larger as a PNG than as a JPG of indistinguishable quality.
PNG also carries a real alpha channel, meaning each pixel records how transparent it is rather than merely whether it is transparent. That is what lets a logo sit on any background without a halo around its edges, and it is the reason PNG remains the default for interface assets three decades after it was designed.
Where it came from
PNG was created in 1995 in direct response to a patent claim on the compression used by GIF. A group of developers on a mailing list specified a replacement in a matter of weeks, unencumbered and technically better in almost every respect, and the web adopted it. The patent expired long ago; PNG outlived the problem it was built to solve.
PNG at a glance
| Property | PNG |
|---|---|
| Compression | Lossless |
| Colour | 8 bits per channel |
| Transparency | Full alpha channel |
| Animation | No |
| Keeps EXIF | Yes |
| Browser support | Every browser since 1997 |
| Size of a photograph | 3 to 5 times a JPG |
| Published | 1996 |
PNG at a glance
- Compression is lossless, so converting between it and another lossless format is a repackaging rather than a re-encoding: nothing is decided and nothing is lost.
- Colour is stored as 8 bits per channel, which is enough for the gradients in a photograph to look smooth rather than stepped.
- Transparency is a full alpha channel: each pixel records how transparent it is, so a soft edge stays soft against any background.
- Camera settings, dates, and copyright fields travel with the image, which matters if you are converting photographs you intend to keep attribution for.
What it is good at
- Full transparency: each pixel records how transparent it is, so edges blend cleanly into any background.
- Nothing is discarded. What you put in is what comes back, however many times you save it.
- Carries camera settings, dates, and copyright information alongside the image.
- Every browser in use reads it, and has for long enough that it needs no fallback.
Where it falls short
- One frame only. An animation converted to it keeps the first frame and drops the rest.
- Roughly 3 to 5 times the size of a JPG of the same photograph at comparable quality.
What to use instead of PNG
- For anything that moves, use animated WebP. GIF also animates and is more widely accepted, but stores the same clip at several times the size with a fraction of the colours.
- For a smaller file at quality most people cannot tell apart, use WebP, or AVIF where the audience is on the web and encoding time is not a concern.
When to use PNG
Choose PNG when the image has sharp edges, flat colour, or transparency: screenshots, logos, icons, diagrams, charts, and anything containing text. Choose it also as a working format when an image will be opened and saved several times before it is finished, because it is the only common raster format that survives that unchanged.
Avoid PNG for photographs. It will produce a file several times larger than a JPG, WebP, or AVIF of the same picture at quality nobody can tell apart, and the extra bytes buy nothing — the photograph has no repetition for PNG's compression to find.
What opens a PNG file
On a computer, PNG files open in Preview on macOS, Photos on Windows, GIMP, Photoshop.
Every browser in use displays them, so opening one is usually a matter of dragging it into a browser window.
Turn a PNG file into something else:
Produce a PNG file from something else:
Common problems with PNG
- The file is far bigger than I expected.
- This format is not built for photographs, and a photograph is what makes it grow: there is no repetition for the compression to collapse. If it is a photograph, JPG, WebP, or AVIF will produce something dramatically smaller at quality most people cannot tell apart.
Converting a PNG file here
- Choose your file, or drag it onto the box. It is read from your device and goes no further.
- Set whatever the conversion offers — quality, size, background — and start it. Everything runs on your own machine, so a large image uses your memory and your processor rather than a queue somewhere.
- Download the result. Nothing is kept: leaving the page or resetting it releases the file and the converted copy alike.
PNG against the alternatives
Common questions
- Why is my PNG so large?
- Almost certainly because it holds a photograph. PNG compresses repetition, and photographs have very little — every pixel differs slightly from its neighbours, so there is nothing to collapse. A photograph belongs in JPG, WebP, or AVIF; PNG is for screenshots, logos, diagrams, and anything with flat areas of colour or text.
- Is PNG better than JPG?
- For different things. PNG is better for anything with sharp edges or transparency and loses nothing when saved repeatedly. JPG is better for photographs, where it produces a far smaller file for quality most people cannot tell apart. Neither is a replacement for the other, which is why both are still here.
- Should I use PNG or WebP for graphics on a website?
- WebP, if you control the markup and the audience is on the web: it is smaller than PNG for the same flat graphic and every browser reads it. PNG remains the safer choice for a file you are handing to somebody else, because desktop support for WebP is still uneven.
- Is transparency kept when I convert a PNG file?
- Only if the format you convert to has somewhere to put it. PNG, WebP, AVIF, and GIF all do, to varying degrees; JPG and BMP do not, and a transparent area becomes a solid colour when you convert to one. The tool tells you which background it used.
- What happens to the camera data and copyright fields?
- They survive where the target format has somewhere to keep them and are dropped where it does not. If attribution matters, check the result rather than assume — metadata is the first thing most conversions lose, and it goes silently.
- How much smaller or larger will the file get?
- The table above states the size of the same photograph in each format against JPG, which is the closest thing to an answer that holds in general. The real figure depends on the picture: flat colour and sharp edges behave very differently from a photograph, and the ranges assume a photograph.
- How do I open a .PNG file?
- The software listed above reads them directly. If nothing on your machine will, converting to PNG or JPG is the reliable route — both open in everything, and the conversion happens here in your browser rather than on a server.
- Does converting a PNG file lose quality?
- It depends on what you convert it to rather than on what you convert from. Converting to a lossless format such as PNG preserves every pixel; converting to JPG, WebP, or AVIF discards detail permanently. Nothing recovers quality the file had already lost.
- Is converting from PNG free, and does it upload my file?
- Free, with no account, and nothing is uploaded. Every converter on this site reads your file with the browser's own file APIs, converts it using code running on your device, and hands the result back as a download. You can confirm that yourself in the Network panel of your browser's developer tools.
- Where does the conversion happen?
- In your browser, on your own device. There is no conversion server here to upload anything to, and no third-party service is involved. That is a statement about what the site does rather than a promise about how it handles uploads, because no upload takes place.