The Sordle currently has four "official" sets:
If you want to, you can also use a custom set, although this is optional.
On the Sordle page, there are two textboxes right above the main grid: one for the set's URL and one for the word separator.
The given URL must point to a page containing only a list of five-letter words separated by the word separator.
For example, if the separator is set to
;, then this would be a valid page for use as a set:
whereas these ones would all be invalid:
Word list: APPLE;BERRY;GRAPE;LEMON;MANGO;OLIVE;PEACH
APPLE BERRY GRAPE LEMON MANGO OLIVE PEACH
The first two lists contain extra content, the third does not use the given separator (it uses a space instead of a semicolon), and the fourth uses a six-letter word. None of them would work properly.