Image Size effects on Site Speed - SEO sustainable
SEO Strategy

Image Size & Site Speed

Site speed, or how fast your webpage loads, has become a major ranking factor in Google’s algorithms. Especially for mobile with the latest Speed Update this year. How fast should a site load? 2 – 3 seconds is the gross generalization that I stick with. But from what Google has told us our web pages simply need to be faster than our slowest competitors.


With that, I brained that if I could find a semi-automated way to reduce image sizes I could protect sites from being negatively impacted by this new ranking factor fro my client’s website.

Optimizing Image Size

First I had to find the best way to optimize the images.

  • Manually Replacing Every Image: This would be me finding the original image and resizing it to the optimum dimensions and then reloading them into the size one by one. A bit time-consuming, to say the least.
  • WordPress Plug-ins: There are s few WordPress plug-ins that offer automatic resizing of images. My favorite is EWWW Image Optimizer. There is a bulk optimization option that will go through all your current images and optimize them for you. Zero manual actions are needed. I have used this on a few sites some personal some professional and it always has been a win. No picture quality has been harmed in the making of these optimations.
  • CDN: This is buying and utilizing a cloud server. It is great if you have the money and DEV resources to do so. Definitely, the way to go if you are enterprise-level. Not so much if you blog from home as a hobby.

I went with option 2, the EWWW plug-in for this project. When  I started her site was 8.5MB. After 19 hours of the EWWW image optimizer working its magic, I got it down to 4.5MB.

Effect on Page Speed

Using Pingdom’s Website Speed Test I got the original site speed of 3.72 s & 43% faster than other pages tested.

Site Speed before Image Optimaztion - SEO sustanable case study

By reducing the image size, just that alone, decreased her load time to 3.04 s and 52% faster than others tested. An improvement of 9% faster than before. It may not seem like much but according to SEJ that could reduce the bounce rate by 62%.

Site Speed after Image Optimazation - SEO sustaianable case study

Effect of Google’s Page Speed Update on Site

This is a Dog DIY Blog that has many many holiday posts on homemade dog treat recipes. For those of you who don’t know about this niche in the pet blogging space, DIY holiday Pet posts are gold in the fall to winter months. I mention this because it is where my ‘it depends’ comes in. January peaks in organic traffic due to seasonal reasons. The Page Speed Update hits and traffic starts to dwindle maybe all from the seasonality of the content? It continues to decline in March & April, now I’m worried it might be from a slow load time. Beginning of May I started optimizing images to improve site speed. The organic traffic stops decreasing and then starts increasing. At the very least I feel comfortable stating that any negative effects she received from Google are no longer an issue.

kol's notes GA traffic site speed

Image Size = Site Speed Conclusion

  1. The size of images does affect site speed.
  2. Even a slight change in speeds, under a second, can have a noticeable effect on organic traffic.
  3. Finding an actionable way to reduce the image size of current images and then all images in the future is the key to making this change sustainable with Google’s ever-changing algorithms.

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