Why my image is not polished to .webp format?


I enable the “Polish” feature as below:

And my browse is the latest version of Chrome.

However, when using Chrome to visit my website https://www.datanumen.com, the images, such as hero.png, are still served as png file instead of webp format.

I have contacted the support of Cloudflare, but their 4 replies are all from " Cloudflare Support Team (Bot) (Cloudflare)", which said " We have run an automated test to your website ( datanumen.com ) and can see that there is a slow response here…", but the answer has no relationship with my question at all.

In the past, when not using Cloudflare CDN, I use Imagify plugin in WordPress and enable “Serve webp format” option, at that time, I can see wep format image is served when I loaded https://www.datanumen.com. Now since I begin to Cloudflare CDN, someone indicates that I should disable the “Serve webp format” option in Imagify and use the Cloudflare Polish option instead.

I see many WebP images:

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It looks like Cloudflare is generating the webp versions and deciding not to serve them, which is most likely because the reduction in file size wasn’t enough to trigger the use of webp. Do you have any large images to check? The largest I saw was just over 20kb.

cf-bgj: imgq:85,h2pri
cf-cache-status: HIT
cf-polished: origFmt=png, origSize=21290
cf-ray: 673885398a4e17cb-MEL
content-disposition: inline; filename=“datanumen-access-repair-38-boxshot.webp”
content-length: 16692
content-type: image/webp

They are being delivered as WebP. Polish does not change the file extension, just the payload.

You will see the underlying file on first request (as Polish delivers the response quickly, while performing the optimisation in the background for the next request). And if the optimisation results in no file size reduction, Polish will also return the original file.


The largest file I can find is hero.png(about 24kb)

I do check the response header for hero.png, and it shows “content-type: image/webp”, as below:

THe problem is that when I save the image into a local file, then open it in hexidecimal editor such as UltraEdit, I see the follow:


The “NG” header indicates the file is still a PNG file, not Webp file.


Just get the reply from Cloudflare support and they confirm the file is served as webp, the “Save as a local file” in browser should just use the URL of the image which still retrieve the PNG data.

Many thanks to all of your helps.


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