July 30, 2026 - Variations of Base64 differ in the alphabet used and structural aspects like maximum line length. The most commonly used alphabet is that described by RFC 4648 and most variations only differ in the last two letters used.

The Base64 Alphabet contains 64 basic ASCII characters which are used to encode data. Yeah, that’s right, 64 characters is enough to encode any data of any length.

JVNJA=== A useful tool that can convert between various numeric bases, including BASE 32 and BASE64, can be found at https://cryptii.com/pipes/base32.

Base64 uses a fixed alphabet of 64 characters.

The base64 uses a sixty-four character alphabet to code any binary string (in base 2), so it is a mathematical conversion to base 64.

February 25, 2026 - The Base64 encoding alphabet contains 64 printable ASCII characters: 26 uppercase letters (A-Z), 26 lowercase letters (a-z), 10 digits (0-9), and 2 symbols (+ and /). The = padding character is not part of the 64-character alphabet.

The particular choice of characters to make up the 64 characters required for Base64 varies between implementations. The general rule is to choose a set of 64 characters that is both 1) part of a subset common to most encodings, and 2) also ...

An alphabet defines the 64 ASCII characters (symbols) used for base64.

Decodes a base64 string encoded using the standard alphabet according to RFC 4648 Section 4 to plain ASCII.

August 8, 2025 - See base64 crate from where these definitions come. ... alphabet("standard") alphabet("bcrypt") alphabet("bin_hex") alphabet("crypt") alphabet("imap_mutf7") alphabet("url_safe") new_alphabet("qwertyuiop[]asdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM1234567890")

This encoding should not be regarded as the same as the "base64" encoding and should not be referred to as only "base64". Unless clarified otherwise, "base64" refers to the base 64 in the previous section. This encoding is technically identical to the previous one, except for the 62:nd and 63:rd alphabet character, as indicated in Table 2.

This includes the encodings specified in RFC 4648 (Base64, Base32 and Base16), the Base85 encoding specified in PDF 2.0, and non-standard variants of Base85 used elsewhere. There are two interfaces provided by this module. The modern interface supports encoding bytes-like objects to ASCII bytes, and decoding bytes-like objects or strings containing ASCII to bytes. Both base-64 alphabets defined in RFC 4648 (normal, and URL- and filesystem-safe) are supported.

July 3, 2026 - MIME Base64 (RFC 2045): Standard alphabet but splits output into 76-character lines with CRLF.

March 19, 2026 - Choosing the wrong variant is one of the most common sources of hard-to-diagnose bugs. The standard alphabet uses A-Z, a-z, 0-9, +, and /. Padding with = is mandatory to ensure the encoded output length is always a multiple of 4.

September 17, 2024 - Base64 is a method of encoding binary data as ASCII text. This is necessary for sending files via Internet email, which can only handle 7-bit ASCII text.

I am interested in the following: Is there a list of characters that would never occur as part of a base 64 encoded string? For example *. I am not sure if this would occur or not. If the original ...

April 29, 2026 - The Base64 alphabet was chosen from a subset of the ASCII character set (A-Z, a-z, 0-9, +, /, =). If you're paying attention very closely, you may have noticed that's actually 65 different values.

August 25, 2025 - Both base-64 alphabets defined in RFC 4648 (normal, and URL- and filesystem-safe) are supported. The legacy interface does not support decoding from strings, but it does provide functions for encoding and decoding to and from file objects. It only supports the Base64 standard alphabet, and it adds newlines every 76 characters as per RFC 2045.

A 64-character alphabet specifying the URI- and filename-safe Base64 alphabet.

When the term "Base64" is used on its own to refer to a specific algorithm, it typically refers to the version of Base64 outlined in RFC 4648, section 4, which uses the following alphabet to represent the radix-64 digits, alongside = as a padding character: