Brr: is it possible to convert a string to an Object URL?

Dumb (on my part) question: independently, I was trying:

external create_object_url_from_blob : Brr.Blob.t -> Brr.Uri.t = "URL.createObjectURL"

however, when I try to call it, I get a runtime error of:

Uncaught (in promise) TypeError: Cannot read properties of undefined (reading 'createObjectURL')

It appears ‘URL’ is undefined for some reason in this case. What am I doing wrong ?