basE91 is an advanced method for converting binary data to ASCII text. It is similar to UUencode or base64, but is much more efficient. The overhead produced by basE91 depends on the input data. It amounts at most to 23% (compare to 33% with base64) and can range down to 14% which typically occurs on 0-byte blocks. This makes basE91 very useful for transferring larger files over binary insecure connections like email or terminal lines.