Christmas lights (also known informally as
fairy lights) are lights used for decoration in preparation for
Christmas and for display throughout
Christmastide. The custom goes back to the use of
candles to decorate the
Christmas tree in Christian homes in
early modern Germany. Christmas trees displayed publicly and illuminated with electric lights became popular in the early 20th century. By the mid-20th century, it became customary to display strings of electric lights as along streets and on buildings Christmas decorations detached from the Christmas tree itself. In the United States, it became popular to outline private homes with such Christmas lights in
tract housing beginning in the 1960s. By the late 20th century, the custom had also been adopted in non-western countries, notably in
Japan and
Hong Kong.