The Yijing (or I Ching) hexagrams are a Chinese divination system dating back nearly 3000 years. As the system produces six results from a binary choice each time, it's equivalent to a six bit number, or one base 64 value. This tool converts Base64 characters into hexagrams, or hexagrams into Base64.
(honestly I created this originally as a shitpost, but hey, it may have its uses)
Base64 includes all capital and lower case English alphabet letters, digits 0-9, and the + and / characters. This tool will automatically convert ? and spaces to /, and , . ! * ' to +. any other characters will be removed when converting.
The hexagram order refers to one of three orders used for the hexagrams. Traditionally, these orders are Fuxi and King Wen. Fuxi is a little-endian binary order, where 1 is a solid line and 0 is a broken line. King Wen order is older, and has a logic lost to time, but it is the order used for unicode characters. "Big Endian" is not a traditional ordering, but a different encoder only used that order, so I'm including it to decode anything that one might encounter using it.
If you want to understand anything that I (Enys, yaodema) post online in a pile of hexagrams, use this tool, with "Order" set to Fuxi; I will not use other orderings, I don't like them much. They're only included for completion's sake!
Happy 'Crypting!