How are the credits counted?
To process an image, a ShortPixel Image Optimization credit is used. Processing an image means smart-cropping (if chosen), resizing and optimization. Once the image was processed, it is stored for 30 days on the ShortPixel servers and it can be served, via CDN, an unlimited number of times during these 30 days.
Once 30 days have passed since the image was first processed, it will be dropped from storage and a new credit will be used to process it again.
Both one-time and monthly credits can be used to optimize images.
Here are some examples:
Simple one-page website with a total of 20 images, each image with 3 associated thumbnails. The thumbnails are served depending on the visitor's viewport. A total of 60 credits will be used each month and there is no need to purchase any plan as the monthly free plan of 100 images is enough to cover the monthly used credits.
A small website with 1,000 images, each with 4 associated thumbnails. The thumbnails are served depending on the visitor's viewport. Each image will be optimized and stored when it is first accessed (by a visitor or by Googlebot, for example). If an older post isn't accessed then no image optimization credit will be used. Up to 4,000 image optimization credits will be needed monthly regardless of how many times the images are accessed. A "SHORT" $4.99 monthly plan will suffice.