Why does Google Chrome save a JPG image to WEBP instead?
File extensions are quite irrelevant for HTTP: if the server says Content-Type: image/webp, then it's a WebP image, period. (Compare to how most websites don't use .html in their URLs anymore even though they serve HTML-based webpages.)
The original image uploaded to the website was an JPEG file; however, it is served to you through a "content delivery network" (Akamai in this case). The CDN's job is to host these files and reduce load on the website's real servers, but many CDNs provide various optimization features to save bandwidth for clients as well – this often includes re-compressing images, minifying JS/CSS files, and so on.
Akamai looks at the HTTP request's User-Agent header to guess what the best format supported by your browser would be (although, oddly, it ignores the Accept header) and automatically converts the image to WebP whenever it wants to. The URL remains the same, but the response's Content-Type header indicates the new format.
Other than installing a "User Agent spoofer" extension or trying a different browser, you could also copy the URL and use the curl or wget tools through Terminal to download it (macOS should have at least one of them built-in). The CDN will usually exempt "non-browser" tools from the webpification feature.
curl -Of https://mosaic03.ztat.net/vgs/media/catalog-lg/NI/12/2O/0H/NQ/12/[email protected]
CDN data traffic reduction
WebP is an image format currently developed by Google, based on technology acquired with the purchase of On2 Technologies.
If the User-Agent field in your HTTP(S) request header reveals you are using a recent browser, content delivery network (CDN) servers may serve original .jpg or .png images in this new WebP format to reduce data traffic. Nonetheless, these served image files will keep their original file extension; what is truly misleading and deceiving.
On GNU/Linux systems, one solution consists in downloading the original image file using either the wget or curl command.
Several Google Chrome extensions offer a way to save images served as WebP in another image format. However, only one extension is open-source software; which is Save image as Type.
This and all other similar extensions have one annoying drawback, though. Between saves, these extensions do not recall the directory to which the previous image was saved. This may or may not be due to Google's sand-boxing policy concerning extensions. Anyhow, I opened a GitHub issue about it.
