Written variant of 免

免 is a variant form of 免, not a separate word.

Older Chinese dictionaries, including the Kangxi Dictionary, record 免 as a written variant of 免. Its upper strokes are shaped like 刀. The early Chinese character dictionary Shuowen Jiezi explains 免 as a rabbit escaping with its feet out of sight; that is a traditional explanation of 免, not a separate meaning for 免.

Unicode kept this exact form so text could be converted to Taiwan’s CNS 11643-1992 character set and back without losing which character it started with. Unicode normalization, a text-cleanup step, can instead map 免 to 免, erasing the distinction.