What is a PNG file?

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PNG (portable network graphic) is a type of image file that's often favoured in web design and creative projects involving Photoshop or similar software. It's a type of file that allows an object to be placed into software with a clear background or as a partially transparent image, making it especially useful when creating a graphic from multiple layers, as is the case in branding and logo design.

PNGs tend to take up more space than alternative image files, so you may want to limit how many you use if storage is an issue. This is because they offer far greater detail and also support grey scale, as well as both the 24-bit RGB and 32-bit RGBA colour spaces. They're not designed to be compatible with CMYK models, though, and it's not recommended to use them when dealing with printed materials. This wider range of supported spaces contributes to the larger PNG file size versus other types.

Another benefit of using PNGs is that they're more easily accessible when it comes to copyright, given they take the form of an open format that can be more widely used without requiring a license. GIF has almost completely replaced PNG in publishing, partly because they're so popular for sharing multi-frame images, and also for compressing down the size of an image file. However, there are more advanced formats for moving images, such as MNGs or multiple image network graphics.

History of PNG

The PNG format was first developed in 1995, at a time when the GIF format was already well established. A more modern file format was needed to keep pace with screen technology, which was becoming capable of supporting a much wider spectrum of colours.

A group of developers then joined forces to create the PNG format and it was decided the new image file should only support a single, static picture. In October 1996, the first iteration of the file format was created, with further versions released in 1998, 1999 and 2003, when it became an international standard.

When to use a PNG

PNG files can sometimes be larger than a GIF and so it's worth considering whether the file format is definitely the best option for the use case. For example, if you have lots of images on one web page, you might want to consider either resizing the image so it's lower quality, or using an alternative image format that results in a smaller file size (for example GIF).

This conversion may result in stripping away the transparency of the image, so if you need to preserve the transparency, PNG is definitely the best option and worth using, even if it's a large file.

How to open and edit a PNG file

PNG files can be opened in any web browser, including Firefox, Chrome, Edge, Safari and Opera, as it's now the most widely adopted web image type. If you don't have an image viewer on your computer, you can even open it by dragging it from your desktop to your browser, although you won't be able to edit it this way.

A PNG file can also be opened and edited in the majority of image editing programs, including Microsoft Paint (despite Microsoft ending support for the bundled image editing program in the very near future), Paint 3D, GIMP, XnView and of course, Adobe PhotoShop.

If you're not sure if you already have an image editor installed on your computer, try double-clicking the image file and any supported program will open it up for you ready to edit.

How to convert a PNG file

You can, of course, convert a PNG file to any other popular format, including JPG, ICO, TIF, BMP and GIF if you wish. This can be done by a whole range of free online converters, including XnConvert, Zamzar, FileZigZag and Adapter.

How to reduce PNG file size

There may be times when you’ll have to reduce the size of your PNG file. For instance, you might be looking for ways to free up some storage on your device or have been asked to send over a specific PNG image in an email. Most email management apps have clear limits on the sizes of files you can transfer, such as 20MB for Outlook or 25MB when using Gmail. With some PNG images being measured in the tens and even hundreds of gigabytes, transferring the file might prove to be a challenge not unlike squeezing water from a stone.


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However, before you choose to convert your PNG image to JPG and call it a day, you might want to explore different ways of simply shaving a few bytes off your file. The internet is rife with different tools which can help you do so, yet you need to know what exactly you’re looking for, or you could risk losing the quality of your file alongside the size. Hence, the free compression tools available online can be divided into two categories: those which quickly reduce your PNG file to the smallest size possible with a cost to its quality, and those which will recompress your file and remove invisible metadata while allowing you to keep the irreplaceable quality of the image. Some examples of the former are online tools TinyPNG and Way2enjoy or command-line tool pngquant. Mac users might want to also consider ImageAlpha, which reduces the size by up to 60% without a noticeable loss in quality. If you’re looking for a tool that will keep your image looking as detailed and colour-rich as possible, consider ImageOptim for Mac, PNGGauntlet for Windows, or Trimage for Linux.

Clare Hopping
Freelance writer

Clare is the founder of Blue Cactus Digital, a digital marketing company that helps ethical and sustainability-focused businesses grow their customer base.

Prior to becoming a marketer, Clare was a journalist, working at a range of mobile device-focused outlets including Know Your Mobile before moving into freelance life.

As a freelance writer, she drew on her expertise in mobility to write features and guides for ITPro, as well as regularly writing news stories on a wide range of topics.