base64-encoding.md

Base64 Encoding

a group of binary-to-text encoding schemes that represent binary data in an ASCII string format

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References

• Base64 - Wikipedia

Intro

In programming, Base64 is a group of binary-to-text encoding schemes that represent binary data (more specifically, a sequence of 8-bit bytes) in an ASCII string format by translating the data into a radix-64 representation.

The term Base64 originates from a specific MIME content transfer encoding. Each non-final Base64 digit represents exactly 6 bits of data. Three bytes (i.e., a total of 24 bits) can therefore be represented by four 6-bit Base64 digits.

2 ^ 6 = 64

Common to all binary-to-text encoding schemes, Base64 is designed to carry data stored in binary formats across channels that only reliably support text content. Base64 is particularly prevalent on the World Wide Web where its uses include the ability to embed image files or other binary assets inside textual assets such as HTML and CSS files.

Base64 is also widely used for sending e-mail attachments. This is required because SMTP — in its original form — was designed to transport 7-bit ASCII characters only. This encoding causes an overhead of 33–36% (33% by the encoding itself; up to 3% more by the inserted line breaks).

Design

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Base64 Table

Index	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	е
31	011111	f
32	100000	g
33	100001	h
34	100010	i
35	100011	j
36	100100	k
37	100101	l
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	/
-	Paddind	=

Examples

= padding characters might be added to make the last encoded block contain four Base64 characters.

Implementations and history

Variants summary table