WebP as source/input images - expected behaviour?

[Peter Knight]

Hi,

I have a question regarding WebP support that I would like to clarify.

I added WebP to my allowed image extensions, and while uploads work fine and the original images display correctly, I'm seeing "not a supported image type" errors when ProcessWire tries to generate thumbnails or variations from WebP source files.

After some digging, I found Ryan's blog post from 2019 which says:
> "WEBP is purely an output format, not an input format... PNG and/or JPG images should still be the standard for any images you upload to your site."

So it sounds like this is expected behaviour - WebP is designed for output (converting JPG/PNG → WebP for delivery) rather than input (uploading WebP and resizing it).

Just wanted to confirm:

• Is this still the case in 2026?
• Is there any plan to support WebP as a source format in the future?
• For those who do allow WebP uploads - do you just accept that variations won't be generated?

For now, I'm working around it by skipping resize attempts on WebP source images and using the originals, which works fine but results in larger file transfers for thumbnails.

Thanks!
Peter

[monollonom]

Did you check https://processwire.com/modules/webp-to-jpg/ ?

[Peter Knight]

Hey thanks for the link. Neat module. Was there a technical or philosophical issue with support for webp as input source image?

[virtualgadjo]

hi,

i guess it may come from the fact that creating a vign (the first variation pw creates when tou upload an image) is not that simple (not possible on a server that only has gd and not a recent imagick version) that would be a not very universal feature so far

have a nice day