Image file formats and when to use PNG

There are various file image formats out there. The most common on the web are JPEGs (extension .jpg or jpeg) and these also come out of most of our cameras and many smartphones (iPhone HEIC format is discussed later). A key attribute is that JPEG supports varying amounts of compression (smaller file size) with imperceivable loss of visual quality. This helps improve website response times.

While the file size of a photograph may not be noticeable on a high-speed home Internet connection, with a mobile connection or a rural home setup load times of uncompressed photographs will be noticeable.

When you upload JPEG photographs to your site WordPress takes care of automatically compressing them. In fact, different sized images will be generated internally so that they look equally good on a full screen home monitor down to a thumbnail image.

PNG files cannot be compressed. If loaded onto SiteWorks then the same image will be displayed for the resolution of a PC monitor as it will for a smartphone. One source of PNGs to be aware of are those generated by AI tools.
PNG images do have their place. As transparent backgrounds are supported by the format a logo or icon can be created to blend into your site whatever background it is placed above. Creating these will be something for your enthusiasts with photoshop type tools.

Already have PNGs on your site? A plugin called “EWWW Image Optimizer” will convert images in the Media library.

Future PNG uploads? If you have content editors who are likely to upload PNGs there is an option you can set for the Imsanity plugin that comes with your SiteWorks configuration. It can automatically convert PNG images to JPEG images. This is a great approach if you have no handy tools to convert images before uploading them. You will find this setting in the WordPress Dashboard ‘Settings > Imsanity’.

HEIC format – be aware that more recent iPhones generate HEIC images by default, a format specific to the Apple universe. This can be changed on the phone through “Settings > Camera > Formats” and selecting “Most Compatible”.