Base64是一種使用64基的位置計數法。它使用2的最大次方來代表僅可列印的ASCII 字元。這使它可用來作為電子郵件的傳輸編碼。在Base64中的變數使用字元A-Z、a-z和0-9 ，這樣共有62個字元，用來作為開始的64個數字，最後兩個用來作為數字的符號在不同的系統中而不同。一些如uuencode的其他編碼方法，和之後binhex的版本使用不同的64字符集來代表6個二進制數字，但是它們不叫Base64。-Base64 is a 64-base position count. It uses the maximum power of 2 to represent the only printable ASCII characters. This makes it available as an e-mail transmission encoding. The variables used in Base64 characters AZ, az and 0-9, so a total of 62 characters used as the starting number 64, the last two used as the sign of the different systems and different. Some other encoding methods such as uuencode and later versions use different binhex 64 character set to represent 6 binary digits, but they are not called Base64.