Base64 Encoder/Decoder

  • Character Set:

Description

Image to Base64 conversion, please refer to Image To Base64
Base64 to Image conversion, please refer to Base64 To Image

ASCII characters occupy 8 bits of binary, while Base64 occupies 6 bits. The least common multiple is 24, meaning 3 ASCII characters can be represented by 4 Base64 characters. With 8 bits per byte, there are 256 states, whereas Base64 characters only have 64 states. Therefore, it's smart to represent 3 binary bytes with every 4 Base64 characters because 64 * 64 * 64 * 64 = 256 * 256 * 256. Since Base64 transforms three bytes into four bytes, the Base64-encoded text will be approximately one-third larger than the original text.

Selecting 64 characters—uppercase letters A-Z, lowercase letters a-z, digits 0-9, symbols "+", "/", and adding "=" as a padding character (in reality, there are 65 characters, and the padding character is added at the end of the Base64 string when the number of generated Base64 characters is not a multiple of 4). Then, all other symbols are converted into characters from this character set.

For example, the string "ABC", whose corresponding binary sequence is 01000001 01000010 01000011, is grouped into 6-bit segments: 010000 010100 001001 000011. Each 6-bit binary segment is prepended with 2 zeros to form a byte, resulting in 00010000 00010100 00001001 00000011. Using the encoding table, this yields the Base64 string "QUJD".

Base64 Encoding Table
Value Binary Char
0 000000 A
1 000001 B
2 000010 C
3 000011 D
4 000100 E
5 000101 F
6 000110 G
7 000111 H
8 001000 I
9 001001 J
10 001010 K
11 001011 L
12 001100 M
13 001101 N
14 001110 O
15 001111 P
16 010000 Q
17 010001 R
18 010010 S
19 010011 T
20 010100 U
21 010101 V
22 010110 W
23 010111 X
24 011000 Y
25 011001 Z
26 011010 a
27 011011 b
28 011100 c
29 011101 d
30 011110 e
31 011111 f
32 100000 g
33 100001 h
34 100010 i
35 100011 j
36 100100 k
37 100101 i
38 100110 m
39 100111 n
40 101000 o
41 101001 p
42 101010 q
43 101011 r
44 101100 s
45 101101 t
46 101110 u
47 101111 v
48 110000 w
49 110001 x
50 110010 y
51 110011 z
52 110100 0
53 110101 1
54 110110 2
55 110111 3
56 111000 4
57 111001 5
58 111010 6
59 111011 7
60 111100 8
61 111101 9
62 111110 +
63 111111 /