I produce html emails on a regular basis in my work.

Recently I've been baffled by the number of promotional emails I receive which use jpeg for images which would be far better served by a png or even a gif.

I've attached some examples from big name brands in the UK: ebay, Cotswolds (an outdoor clothing company) and The Guardian. They all include images with large areas of flat colour that would show less quality degredation/artefacting and have smaller file sizes if they had been saved as a png. Cotswolds even have their logo saved as a jpeg!

Is there a reason I'm not aware of that digitally savvy companies would use jpeg in these circumstances?

As far as I am aware, png is well supported in all major email clients these days. I understand using a jpeg for a photograph - but not a logo.

enter image description here

EDIT: With regards to file size, it is a misconception that jpeg is smaller.

For image like these (with large areas of flat colour), png will have a smaller file size. Jpeg was designed for photographs.

I saved an image of this style as a png, and a jpeg at the lowest file size possible via photoshop. The png is only 13.7kb. The jpeg is 20kb. The png is around 30% smaller.

JPG enter image description here

  • I'm closing this question as off-topic because it is not about running your website. – Stephen Ostermiller Oct 25 '17 at 16:47
  • "png is well supported in all major email clients these days" - I think you may have answered your own question. Yes, PNG is supported by "major [read: modern] email clients", but for legacy support you may still need to resort to JPGs. Depends on your target audience. – MrWhite Oct 26 '17 at 11:03

Typically a jpeg is smaller in file size. With a jpeg you can select the level of compression however this can sometimes degrade the image.

I only use png images when I wish the image to have a transparent background as it is lossless, therefore larger in file size. Using jpeg for for an image produces a smaller file meaning it is faster to load.

  • Agreed with Matthew, jpg is generally the goto format for optimised solutions not just on emails but on web too. PNG's I tend to use for transparency or on images i require a greater quality for and the cost/size of the files don't matter – Randomer11 Oct 25 '17 at 15:41
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    I have to disagree here. png and jpeg are designed for different uses. I have edited my post to include some pictures I created for comparisons sake. The png is 30% smaller in file size. – Rhys Mills Oct 25 '17 at 15:47
  • You can go much smaller with both file types in your comparison. The PNG should be below 4kb really with no quality loss. Like this : i.imgur.com/xLv7XJ3.png But you are correct images have different compatible compressions for file type usage. – Randomer11 Oct 25 '17 at 15:58
  • You're not wrong when you say they could be smaller in png, this is why I state this is typically the case. Most people who produce content for the web will only be aware of the basics of compression. I would imagine they've used jpeg because they've been told that's what you should use for the web without knowing any fundamentals behind the technology. – Matthew Jasek Oct 25 '17 at 16:02

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