Why are there image.jpg.webp files instead of image.webp files on my disk?

If ShortPixel Image Optimizer (SPIO) is creating WebP files with the extension .jpg.webp instead of .webp, this could be because:

1. You have two images with the same identical filename but different extensions. For example, image.png and image.jpg. In this case, SPIO will need to create one of the WebP files with a double extension to distinguish one from the other.
2. There was already a WebP file existing on the disk, and therefore, while optimizing the image, SPIO had to create a .jpg.webp version in order to avoid overwriting it.
3. You have added the constant SHORTPIXEL_USE_DOUBLE_WEBP_EXTENSION in your wp-config.php file. For more information: List of constants to add in wp-config.php.