Base64 Decode

Base64 Decode is a free decoder for decoding online Base64 to text or binary. In other words, it is a tool that converts Base64 to original data. This online decoder is as smart as it is simple. Its superpower is the ability to automatically detect the encoding standard.

Base64 Encode, a simple online tool. Base64 decode your data without hassles and into a human-readable format.

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FAQs

Q.: What is Base64 encoding?

A.: The term Base 64 is generic, and there are many implementations. MIME, which stands for Multi-Purpose Internet Mail Extensions, is the most common that is seen today. It is used to transmit attachments via email over the Simple Mail Transfer Protocol (SMTP). Other examples of Base64 encoding are Radix-64 and YUI's Y64. Encoding data in Base64 results in it taking up roughly 33% more space than the original data.

Q.: When and why would you use Base64 encoding?

A.: You should use Base64 whenever you intend to transmit binary data in a textual format.

Q.: Base64 Characters

A.: 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. The only drawback is that the size of the result will increase to 33%. However, its benefits are much more important, at least because all these symbols are available in 7-bit and 8-bit character sets.

Characters of the Base64 alphabet can be grouped into four groups:

  • Uppercase letters (indices 0-25): ABCDEFGHIJKLMNOPQRSTUVWXYZ
  • Lowercase letters (indices 26-51): abcdefghijklmnopqrstuvwxyz
  • Digits (indices 52-61): 0123456789
  • Special symbols (indices 62-63): +/
Index Binary Char Index Binary Char Index Binary Char Index Binary Char
0 000000 A 16 010000 Q 32 100000 g 48 110000 w
1 000001 B 17 010001 R 33 100001 h 49 110001 x
2 000010 C 18 010010 S 34 100010 i 50 110010 y
3 000011 D 19 010011 T 35 100011 j 51 110011 z
4 000100 E 20 010100 U 36 100100 k 52 110100 0
5 000101 F 21 010101 V 37 100101 l 53 110101 1
6 000110 G 22 010110 W 38 100110 m 54 110110 2
7 000111 H 23 010111 X 39 100111 n 55 110111 3
8 001000 I 24 011000 Y 40 101000 o 56 111000 4
9 001001 J 25 011001 Z 41 101001 p 57 111001 5
10 001010 K 26 011010 a 42 101010 q 58 111010 6
11 001011 L 27 011011 b 43 101011 r 59 111011 7
12 001100 M 28 011100 c 44 101100 s 60 111100 8
13 001101 N 29 011101 d 45 101101 t 61 111101 9
14 001110 O 30 011110 e 46 101110 u 62 111110 +
15 001111 P 31 011111 f 47 101111 v 63 111111 /
Padding =

Q.: How does Base64 encoding algorithm work?

A.: Base64 encoding is multi-step process. But it is very simple. Here is how it works -

  1. Convert the input to 8-bit bytes
  2. Re-group the input to 6-bit groups.
  3. Find the decimal equivalent of the 6-bit groups.
  4. Use the Base64 alphabet table to find the character corresponding to the decimal values.
  5. If the input can’t be grouped into an integral number of 6-bit groups, then one or two pad character is added to the output based on the following conditions:
    • If the last group contains 2 bits, append 4 zero bits to the input.
    • If the last group contains 4 bits, append 2 zero bits to the input.

Let’s see an example:

Input: @!
8-bit bytes: 01000000 00100001
6-bit groups: 010000 000010 000100
Decimal values: 16 2 4
Base64: Q C E
Final output: QCE=