Image Size Resource

AMAZON:

At least 1000 pixel on either height or width

https://www.amazon.com/gp/help/customer/display.html?nodeId=202073580

Etsy: 

The recommended size for listing images is 2000px for the shortest side of the image, and a resolution of 72PPI. File < 1MB for smooth uploading.

https://help.etsy.com/hc/en-us/articles/115015663347-Requirements-and-Best-Practices-for-Images-in-Your-Etsy-Shop?segment=selling

Instagram:

  • The ideal size for square posts is 1080px by 1080px at a 1:1 aspect ratio.

  • For landscape posts, use an image that is 1080px by 566px, with an aspect ratio of 1.91:1.

  • Vertical images should be sized at 1080px by 1350px with a 4:5 aspect ratio

https://www.adobe.com/express/discover/sizes/instagram​

Ebay:

The API supports a maximum image dimension of 15,000 pixels (width + height in pixels). If your image is less than 1,000 pixels (width + height in pixels), a warning is provided but the picture is not rejected.

For the best zoom-in functionality, size your images so they are between 800-1600 pixels on the longest side.

https://developer.ebay.com/devzone/merchant-products/catalog-best-practices/content/images.html#:~:text=Image%20sizing%20and%20formats,-Image%20dimensions%3A%20The&text=For%20the%20best%20zoom%2Din,image%20must%20not%20exceed%2012MB.

Squarespace:

Recommend using images that are between 1500 and 2500 pixels wide

https://support.squarespace.com/hc/en-us/articles/206542517-Formatting-your-images-for-display-on-the-web

Wix:

A resolution of at least 3,000px on the shortest side of your picture

https://www.wix.com/blog/photography/2017/02/20/how-to-optimize-images-for-website/