knowledge/technology/files/Base64.md

obj	wiki	rfc
concept	https://en.wikipedia.org/wiki/Base64	https://datatracker.ietf.org/doc/html/rfc4648

Base64

Base64 is a group of similar binary-to-text encoding schemes that represent binary data in an ASCII string format by translating it into a radix-64 representation.

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:

ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/

A common variant is "Base64 URL safe", which omits the padding and replaces +/ with -_ to avoid characters that might cause problems in URL path segments or query parameters.

Base64 encoding schemes are commonly used to encode binary data for storage or transfer over media that can only deal with ASCII text (or some superset of ASCII that still falls short of accepting arbitrary binary data). This ensures that the data remains intact without modification during transport. Common applications of Base64 include:

• Email via MIME
• Storing complex data in XML
• Encoding binary data so it can be included in a Data URL

Alphabet

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	e
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	/
Padding	-	=