Creates a URL-safe string of text from otherwise unsafe text. If you wanted to create a service from this, open an Automator project that grabs the clipboard content, then run this AppleScript on said clipboard content, then re-copy the output the clipboard again.

Slugify.applescript

# What is this?
# This AppleScript takes as input the clipboard content [that is potentially unsafe-for-URLs string of text] (such as a blog post in Title Case)
# The script then creates a URL-safe version
# For example: `This Is a Title of a Post!` --> `this-is-a-title-of-a-post`
# Boomshakalaka

# This is from https://superuser.com/questions/635351/process-clipboard-content-on-mac-os

# You can create an Automater service as well: https://d.pr/i/xtX7kN+

# The workflow:
# 1) Select text
# 2) Copy to clipboard
# 3) Run Slugify.workflow (as a Service in macOS `~/Library/Services`)
# 4) Paste converted text

set theclip to the clipboard contents
on normalize(the_string)
  set p_script to ¬
    "# -*- coding: utf-8 -*-
import unicodedata, sys

def normalize(x):
    normal_form_1 = 'NFKD'
    normal_form_2 = 'NFC'
    x = unicodedata.normalize(normal_form_2, x)
    x = x.lower()
    x = x.replace(u'ß', u'ss')
    x = x.replace(u'å', u'aa')
    x = unicodedata.normalize(normal_form_1, x)
    x = u''.join([c for c in x if not unicodedata.combining(c)])
    x = x.encode('utf-8')
    return x
arg = sys.argv[1].decode('utf-8')
x = normalize(arg)
print x"
  
  set p_script to quoted form of p_script
  set the_string to quoted form of the_string
  
  return (do shell script ("python -c " & p_script & " " & the_string))
end normalize
on change_case(this_text)
  set the comparison_string to "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
  set the source_string to "abcdefghijklmnopqrstuvwxyz"
  set the new_text to ""
  repeat with this_char in this_text
    set x to the offset of this_char in the comparison_string
    if x is not 0 then
      set the new_text to (the new_text & character x of the source_string) as string
    else
      set the new_text to (the new_text & this_char) as string
    end if
  end repeat
  return the new_text
end change_case
on replace_chars(this_text, search_string, replacement_string)
  set AppleScript's text item delimiters to the search_string
  set the item_list to every text item of this_text
  set AppleScript's text item delimiters to the replacement_string
  set this_text to the item_list as string
  set AppleScript's text item delimiters to ""
  return this_text
end replace_chars

# Alex had a bunch of special characters getting converted to their URL-safe versions. Since my desire was to just create clean filenames, I actually wanted to remove those characters entirely
set theresult to normalize(theclip)
set theresult to replace_chars(theresult, " ", "-")
set theresult to change_case(theresult)
set theresult to replace_chars(theresult, "%", "")
set theresult to replace_chars(theresult, "<", "")
set theresult to replace_chars(theresult, ">", "")
set theresult to replace_chars(theresult, "#", "")
set theresult to replace_chars(theresult, "{", "")
set theresult to replace_chars(theresult, "}", "")
set theresult to replace_chars(theresult, "|", "")
set theresult to replace_chars(theresult, "\\", "")
set theresult to replace_chars(theresult, "^", "")
set theresult to replace_chars(theresult, "~", "")
set theresult to replace_chars(theresult, "[", "")
set theresult to replace_chars(theresult, "]", "")
set theresult to replace_chars(theresult, "`", "")
set theresult to replace_chars(theresult, ";", "")
set theresult to replace_chars(theresult, "/", "")
set theresult to replace_chars(theresult, "?", "")
set theresult to replace_chars(theresult, ":", "")
set theresult to replace_chars(theresult, "@", "")
set theresult to replace_chars(theresult, "=", "")
set theresult to replace_chars(theresult, "&", "")
set theresult to replace_chars(theresult, "$", "")
# I added the following three replacements
set theresult to replace_chars(theresult, ",", "")
set theresult to replace_chars(theresult, "'", "")
set theresult to replace_chars(theresult, "\"", "")