Please remember when saving images to upload to the web – photos should be saved as JPGs.
PNG is another popular format for the web but it works best on images like logos, with large blocks of the same colour.
Anything like a photograph that is made up of 1000s of different colours will always be best as a JPG – and usually about one 10th the filesize.
Of the clients that ask me to speed up their WordPress websites (in addition to their SEO work) perhaps the most improvement comes from simply converting their photos they’ve saved as PNGs into JPGs. If a site has several photos that are saved as the wrong file type it’s easy to shave several megabytes off the page size, and therefore speed up the site’s loading time.
Part of the problem is a lot of software for editing images will default to PNG when you use their “Save for web” function. Which is fine for icons and logos, charts and even text saved as an image.
So many websites these days focus on really high quality imagery (understandably – people love photographs!) but don’t know that not all file types are created equally, they all have different purposes and use cases and those wonderful product shots should always be saved as JPGs.
It’s good to get in the habit of doing this right away – after an image is uploaded into WordPress there’s no simply way to convert it to JPG and change all the references in the code to use the different filename. So try to get it right from the outset!