Adam Silverstein

I would say use WebP for now until you can get your server upgraded. Once WordPress detects AVIF support you will be able to use it.

Try one of these: https://www.ads-software.com/plugins/tags/regenerate-thumbnails/

It should be displayed in the browser, unless you are linking to your original image (instead of a size like large). You could also try WebP to make sure it isn’t a format issue.

which library (libheif or libavif) you used

this depends on your web server where the image is processed, and how it was built/configured. WordPress supports GD and Imagick out of the box and these libraries are used to generate the AVIF images.

the default speed (0 or 10) and quality (1 or 100%)

Speed: 7 Quality 82

so I’m not 100% sure images which previously were generated to as AVIF would then get re-generated as WebP. @adamsilverstein would know better.

They would be as long as when you chose to regenerate all images (both the plugin and CLI offer options to control this). You can also choose to leave the old images around or delete them.

Thanks for the update Jack, I will try to reproduce this again.

Hi @j43l35 & @senator94 –

Uploaded AVIF should output AVIF if you have it set to output AVIF in Settings->Media and if your server supports AVIF. I will. double check that this is working/mapped correctly

Please check if your server supports AVIF, this is required when uploading any format to create the sub-sized images in AVIF. See Tools->Site Health->Info->Media and look for AVIF.

Hi @vegisto –

– I regenerate the thumbnails for e.g. one picture

What tool are you using to regenerate the thumbnails?

Location:?https://<domain>/wp-content/uploads/2025/01/855_Artischocken_Ravioli-1140×450.jpg

is this the “original” image you uploaded? please note that regenerating thumbnails generally only generates sub-sized images (thumbnail, medium, large, etc.), the original uploaded image is not touched.

Are you using AVIF output or WebP output?

Finally, can you check your media support under Tools->Site Health->Info->Media – it is possible your server doesn’t support the format you are trying to regenerate into.

How can you explain this fairly significant difference? Don’t you use the same compression ‘technologies’?

Thanks for the bug report.

While both Squoosh and your Web Server running WordPress both likely use the same “libavif” library under the hood, they may use different versions or have different settings.

libavif has improved over time so you may be seeing the results of that in your tests (newer versions do a better job compressing images). There are also numerous settings that can be set that might change the quality, for example the “speed” or effort the compressor expends when processing the image (try checking under advanced settings in Sqoosh).

Hi ?ngelo,

The message you are seeing indicates WordPress is not detecting AVIF support. Can you try visiting Tools->Site Health->Info and taking a screen shot of the Media section, this will give us a view of how WordPress sees your image support.

This may be to the version of Imagick you server uses – you can check the version under Tools->Site Heakth->Info->Media – could you post a screenshot of your setup on the ticket linked above, that might help pinpoint the issue.

Note that Imagick::getImageAlphaChannel() is only available if Imagick has been compiled against ImageMagick version 6.4.0 or newer.

If not, I’ll go back to WebP.

makes sense! If you find you do have an old Imagick library, your web host may be able to upgrade it (since its a drop-in library), I would suggest opening a ticket with them describing the issue.

@mkautsarjuhari what tool did you use to regenerate images? When regenerating images, there is usually an option to leave the old images in place which you want to keep checked if you have references to these images that would break if the image filenames changed.

This should be fixed in WordPress 6.7, see https://core.trac.www.ads-software.com/ticket/61614.

Hi @loanpaye –

You can use the webp_uploads_upload_image_mime_transforms filter to add additional mime transforms.

Something like:

add_filter( webp_uploads_upload_image_mime_transforms function( $transforms ) { 
    $transforms['image/png'] = 'image/webp';
    return $transforms;
} );

• This reply was modified 1 year, 5 months ago by Adam Silverstein.

Hi @sanne65 can you try the latest version to see if it works now, the previous version had a breaking bug.