Is there an encoding that is less wasteful that base64 but not vulnerable to text editor corruption issues? I think avoiding 0x0 to 0x20 should be enough to not get corrupted by text editors, though base64 avoids a lot more than that.
If you can count on every printable ascii character being not-mangled, you can use ascii85/base85/Z85 (5 "ascii characters" to 4 bytes) instead of base64.
While a couple of people suggested Base65536, that encoding isn't particularly compact, and it can't be as elegant as 65536 would suggest because it has to dodge special cases in unicode.
It's almost always the case that either Base32768 is denser, or encodings with 2^17 or 2^20 characters are denser.
if you mean the thing you want to encode is mostly-ascii, then https://en.wikipedia.org/wiki/Quoted-printable ... it's a real throwback, I've not seen this in the wild since the 90s, but it's there in the python standard library (quopri), perl (MIME::QuotedPrint) etc
