Since not all strings have lengths evenly divisible by three, base64 encoding requires some padding when there aren’t enough bytes for encoding. This works out well because there were exactly 24 bits, or three ASCII characters, to encode. a-G-F-0Īnd so the base64 encoded form of “hat” is “aGF0″. Then, replace each number with it’s character from the base64 alphabet.

To convert into base64 encoding, take this and redefine the boundaries to be 6 bits: 011010-000110-000101-110100Īfter that, convert each 6 bits into a number. In order to base64 encode data, you need at least 24 bits (the smallest number that’s equally divisible by 6 and 8), so any three-character ASCII sequence can cleanly be encoded in base64. The 6-bit number 0 therefore is represented by the letter A in a base64-encoded string, the 6-bit number 1 is represented by B, and so on. The 65th character is the equals sign (=) and that is used to indicate padding (discussed later). There are 65 possible characters in the base64 alphabet: the letters A through Z, a through z, the numbers 0 through 9, the plus sign (+) and the slash (/). Base64 encoding is really nothing more than performing this conversion. Each character in the string is represented by a single 8-bit byte each character in a base64-encoded string is made up of just 6 bits. You don’t really base64 encode strings, you base64 encode the bytes representing the characters that make up strings. How does it work?īase64 encoding works directly on the underlying binary representation of data. In short, these encodings were created to protect against data corruption when 8-bit data might be transmitted through or by 7-bit systems. Email traditionally was a 7-bit system, and MIME base64 encoding was originally defined to enable data to safely be transmitted from one system to the next.

Base64 encoding provides no encryption, it simply translates one form of data into another following a single algorithm.Īll three encodings, base16, base32, and base64 were defined so that data could be transmitted in a safe manner without risk of data loss when passed through 7-bit systems. A common and unfortunate misconception is that base64 encoding is an encryption algorithm designed to obscure the underlying data. Base64 encoding is described in RFC 3548, along with base16 and base 32 encodings, all of which are ways to represent single-byte data with a limited character set. A key part of the data URI equation is base64 encoding. Not too long ago, I wrote about data URIs and released a couple of tools to help generate them.

Base64 encoding javascript