Modifying the end of a URL using formula

Hi everyone,
I’m really sorry for that (probably) stupid question but I can’t get a valid answer to my issue by searching alone ;(

I would like to be able to use a formula to replace :

I just want to remove the end of the URL because the formating of the begining could change.

Thanks for your precious help :pray:

I’ve made that
( NOT({Favicon} = ‘’), CONCATENATE(LEFT({Favicon},LEN({Favicon})-11), ‘.jpg’), ‘’)

I think it’s correct ?