free-to-use (ie public domain or copyright-free) meaning the words can be copied and sung, to at least one tune, with no concerns about copyright or performance licensing.
"Well-known" is a very subjective: this list has been compiled by scanning Christmas lists published on the internet by various parishes in the English-speaking world, and choosing the carols which appear across multiple parishes and countries.
Adeste Fideles / O Come all ye Faithful
Angels We Have Heard on High
Away in a Manger
Go Tell it on the Mountain
Hark! The Herald Angels Sing
It Came Upon the Midnight Clear
Joy to The World
O Little Town of Bethlehem
O Holy Night
The First Nowell
The Virgin Mary had a Baby Boy
What Child is This
Are there other carols which you believe are so well-known that they should e on this list? Or ones on the list which you think are not well-known and don't be long here? Please share the details in this comments section at the bottom of the page