Here is an AppleScript that will prompt you for the source folder containing the .webp images and for a destination folder where the converted jpg images are written. It then loops through all discovered .webp images and performs the conversion at 100% JPG quality.
Tested: macOS Tahoe 26.1.
Click on the Desktop and enter shift+cmd+U to open the Utilities folder. Double-click Script Editor to launch it, and choose New document on your Desktop. Now, copy/paste the following code into the Script Editor:
use scripting additions
-- select folder containing webp images first, then destination folder
-- for the converted jpg images
set afolder to (choose folder with multiple selections allowed)
set srcFolder to POSIX path of (first item of afolder) as text
set dstFolder to POSIX path of (last item of afolder) as text
set args to quoted form of srcFolder & space & quoted form of dstFolder
my webp2jpg(args)
display dialog "Script done. Check your destination JPG folder."
return
on webp2jpg(args)
return (do shell script "zsh -s <<'EOF' - " & args & " >& /dev/null" & "
#!/bin/zsh
SRCFOLDER=${1}
DSTFOLDER=${2}
setopt nocaseglob
for f in ${SRCFOLDER}/*.(webp)(.N);
do
/usr/bin/sips -s format jpeg -s formatOptions 100 -o ${DSTFOLDER}/${f:r:t}.jpg \"${f}\"
done
")
end webp2jpg
Click the hammer icon on the Script Editor toolbar to compile the just pasted code, and then click Run. Ideally, your source and destination folders should be in the same location, so you can click one, press and hold the command key, and select the destination folder. The script will run quickly and inform you when it is done.
