"The web server cannot generate responsive image sizes for this image" in WordPress.

Error "The web server cannot generate responsive image sizes for this image. Convert it to JPEG or PNG before uploading.» / «The web server cannot generate adaptive image sizes for this image. Convert it to JPEG or PNG before uploading it." (code "rest_upload_image_type_not_supported") appears in WordPress version 6.8 or higher in case you have a not installed required PHP modules for image processing, and you upload an image in WebP format, for example. You can verify this by going to "Tools" -> "Site Health" in the admin panel:

If you see a similar message here:

So you need to:

• Add support for at least the gd module in PHP on your server
• Or roll back to WordPress versions below 6.8 (not recommended).

If you are uploading an image in SVG format (not via ClipAI), you probably need to install the plugin Safe SVG.