[Smush Pro] CDN serves unsupported webp images to IE11

Smush CDN is serving webp images to IE11 which doesn’t support this format. Please check.

  • Adam Czajczyk
    • Support Gorilla

    Hello johnol

    I hope you're well today and than you for your question!

    I just checked your site with Internet Explorer 11 and also tested this on my own test site and in both cases images were displayed. This is a screenshot from the homepage of your site taken from IE11 on Windows 10:

    The screenshot also includes a view of the page source as I wanted to double-check this. What should happen, and seems to be happening, is that the CDN serves the WebP images to browsers that support it but if it detects browser that doesn't support that format (and you are right, Internet Explorer 11 does not) there's a fallback to PNG or JPG (depedning on the original format).

    You mentioned that you had a number of the reports of missing images, I'm wondering whether it's still happening (so it'd be "only me" seeing them properly) or if it actually started to work (which could suggest just a matter of cache). Can you confirm for sure that all the reports are regarding IE11 and not older IE versions and also is there any chance to get to know on what Windows versions that was reported?

    Kind regards,


  • Predrag Dubajic
    • Support

    Hi johnol,

    Apologies for the long delay here, we’ve been a bit short staffed last couple of days and we’re doing our best to bring everything back to normal now.

    I tried doing some tests on my end since you have disabled CDN on your site but I couldn’t replicate the issue with my test site on IE11.

    Would you mind granting us support access to your site so we could temporarily enable CDN in order to test this out further?

    To enable support access you can follow this guide here:


    Please respond in this ticket once access is granted.

    Best regards,


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