There’s something else going on there besides base64 encoding of the URL – possibly they have some binary tracking data or other crap that only makes sense to the creator of the link.

It’s not hard to write a small Python script that gets what you want out of a URL like that though. Here’s one that works with your sample link:

#!/usr/bin/env python3

import base64
import binascii
import itertools
import string
import sys

input_url = sys.argv[1]
parts = input_url.split("/")
  
for chunk in itertools.accumulate(reversed(parts), lambda b,a: "/".join([a,b])):
  try:
    text = base64.b64decode(chunk).decode("ascii", errors="ignore")
    clean = "".join(itertools.takewhile(lambda x: x in string.printable, text))
    print(clean)
  except binascii.Error:
    continue

Save that to a file like decode.py and then you can you run it on the command line like python3 ./decode.py ‘YOUR-LINK-HERE’

e.g.

$ python3 ./decode.py 'https://link.sfchronicle.com/external/41488169.38548/aHR0cHM6Ly93d3cuaG90ZG9nYmlsbHMuY29tL2hhbWJ1cmdlci1tb2xkcy9idXJnZXItZG9nLW1vbGQ_c2lkPTY4MTNkMTljYzM0ZWJjZTE4NDA1ZGVjYSZzcz1QJnN0X3JpZD1udWxsJnV0bV9zb3VyY2U9bmV3c2xldHRlciZ1dG1fbWVkaXVtPWVtYWlsJnV0bV90ZXJtPWJyaWVmaW5nJnV0bV9jYW1wYWlnbj1zZmNfYml0ZWN1cmlvdXM/6813d19cc34ebce18405decaB7ef84e41'
https://www.hotdogbills.com/hamburger-molds/burger-dog-mold

This script works by spitting the URL at ‘/’ characters and then recombining the parts (right-to-left) and checking if that chunk of text can be base64 decoded successfully. If it does, it then takes any printable ASCII characters at the start of the string and outputs it (to clean up the garbage characters at the end). If there’s more than one possible valid interpretation as base64 it will print them all as it finds them.