Base64 Character Set: 64 Characters and Their Origin
Explore the 64 characters used in Base64 (A–Z, a–z, 0–9, +, /) and why this specific set is safe for text-based protocols like SMTP and HTTP.
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Tags: encoding, developer-tools, base64
Base64 Character Set: The 64 Characters and Why They Were Chosen Base64 encoding uses exactly 64 characters to represent arbitrary binary data as printable text. The choice of those 64 characters wasn't arbitrary — it reflects the constraints of 1970s–80s computing infrastructure and the need for universal compatibility across systems that might corrupt or drop certain bytes. The Complete Base64 Alphabet The standard Base64 alphabet, defined in RFC 4648, consists of: | Range | Characters | Count | |---|---|---| | Uppercase letters | A B C D E F G H I J K L M N O P Q R S T U V W X Y Z | 26 | | Lowercase letters | a b c d e f g h i j k l m n o p q r s t u v w x y z | 26 | | Digits | 0 1 2 3 4 5 6 7 8 9 | 10 | | Special | + / | 2 | | Total | | 64 | Plus the padding character , which isn't…
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