Hi Igor, Use a regular expression in a copy and replace action in a modification template. The documentation you linked to has an example if you scroll down (see "You could also use regular expressions to add your library’s proxy URL in front of links in your MARC record."). Note that if you have multiple 856 fields in a record the templates may struggle to process both, or at least I have found that sometimes I need to bulk modify records with pymarc or MarcEdit outside Koha in these instances. Best, ERIC PHETTEPLACE Systems Librarian, Libraries (he/him) ephetteplace@cca.edu *CCA is situated on the traditional unceded lands of the **Chochenyo and Ramaytush Ohlone** peoples.* Black-owned bookstores in Oakland: Ashay by the Bay <https://ashaybythebay.com/>, Marcus Books <https://www.facebook.com/marcus.books/> :(){ :|: & };: