Encode and Decode Base64 Online

Tips and Tricks

Drag and Drop: Drag a file to quickly convert it
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URL shortcuts: You can link to this site to encode or decode a specific input, like https://base64.run/hello world or https://base64.run/aGVsbG8gd29ybGQ=. Encoded URI components will be decoded.

About Base64

Base64 encoding is a convenient, portable way of representing data.

Use For Web Development

Base64-encoded copies of images, CSS, fonts, and JavaScript can be used in places where you would otherwise reference a URL. This can be useful for removing dependencies on external files, to reduce the number of network requests or to allow a document to exist on its own.

This uses the 'data URI' format. The URI is of the format data:${mediatype};base64,${data}, where

${mediatype} is a media type (also known as a 'MIME type'), documenting the type of file, probably one of image/jpeg, image/png, image/gif, text/javascript, text/css, font/opentype;charset=utf-8, application/font-woff;charset=utf-8, application/font-ttf;charset=utf-8;
;base64, has been added after the media type to denote how your data has been encoded; and
${data} is the Base64 encoded contents of the file you're embedding.

ASCII characters

ASCII is a standard for representing 128 different characters: capital and lowercase letters, numbers, common punctuation, spaces, and some control instructions used by computers to understand documents.

This means that each of these supported characters can also be represented as a number. For example, 'A' is always '65', and 'h' is always '150'. Any system that uses this standard knows how to make this translation, and so these characters can be encoded to numeric representations and processed by computers, and shared between systems that all understand this way of representing supported characters.

The ASCII character set
	_0	_1	_2	_3	_4	_5	_6	_7	_8	_9	_A	_B	_C	_D	_E	_F
0_	NUL0000	SOH0001	STX0002	ETX0003	EOT0004	ENQ0005	ACK0006	BEL0007	BS0008	HT0009	LF0010	VT0011	FF0012	CR0013	SO0014
1_	DLE0016	DC10017	DC20018	DC30019	DC40020	NAK0021	SYN0022	ETB0023	CAN0024	EM0025	SUB0026	ESC0027	FS0028	GS0029	RS0030	US0031
2_	SP0032	!0033	"0034	#0035	$0036	%0037	&0038	'0039	(0040	)0041	*0042	+0043	,0044	-0045	.0046	/0047
3_	00048	10049	20050	30051	40052	50053	60054	70055	80056	90057	:0058	;0059	<0060	=0061	>0062	?0063
4_	@0064	A0065	B0066	C0067	D0068	E0069	F0070	G0071	H0072	I0073	J0074	K0075	L0076	M0077	N0078	O0079
5_	P0080	Q0081	R0082	S0083	T0084	U0085	V0086	W0087	X0088	Y0089	Z0090	[0091	\0092	]0093	^0094	_0095
6_	`0096	a0097	b0098	c0099	d0100	e0101	f0102	g0103	h0104	i0105	j0106	k0107	l0108	m0109	n0110	o0111
7_	p0112	q0113	r0114	s0115	t0116	u0117	v0118	w0119	x0120	y0121	z0122	{0123	\|0124	}0125	~0126	DEL0127

Because computers today typically work in multiples of 8 bits at a time, there is room for 256 characters. This extra room gives space for more characters, and is referred to as EASCII, or 'Extended ASCII'

There are several distinct encoding patterns for EASCII, so systems encoding or decoding characters to numbers need to agree on which numbers represent which characters. The most prevalent system is called 'Latin-1'.

The Latin-1 extended ASCII character set
	_0	_1	_2	_3	_4	_5	_6	_7	_8	_9	_A	_B	_C	_D	_E	_F
A_	NBSP 160	¡ 161	¢ 162	£ 163	¤ 164	¥ 165	¦ 166	§ 167	¨ 168	© 169	ª 170	« 171	¬ 172	SHY 173	® 174	¯ 175
B_	° 176	± 177	² 178	³ 179	´ 180	µ 181	¶ 182	· 183	¸ 184	¹ 185	º 186	» 187	¼ 188	½ 189	¾ 190	¿ 191
C_	À 192	Á 193	Â 194	Ã 195	Ä 196	Å 197	Æ 198	Ç 199	È 200	É 201	Ê 202	Ë 203	Ì 204	Í 205	Î 206	Ï 207
D_	Ð 208	Ñ 209	Ò 210	Ó 211	Ô 212	Õ 213	Ö 214	× 215	Ø 216	Ù 217	Ú 218	Û 219	Ü 220	Ý 221	Þ 222	ß 223
E_	à 224	á 225	â 226	ã 227	ä 228	å 229	æ 230	ç 231	è 232	é 233	ê 234	ë 235	ì 236	í 237	î 238	ï 239
F_	ð 240	ñ 241	ò 242	ó 243	ô 244	õ 245	ö 246	÷ 247	ø 248	ù 249	ú 250	û 251	ü 252	ý 253	þ 254	ÿ 255

The ASCII standard most easily supports English words and punctuation. Extended ASCII encodings can add on support for characters of other languages, but 128 additional characters isn't enough to represent an alphabet in every language.

Consider the number of variations in writing systems with heavy diacritic use, like Vietnamese's tonal marks; or logographic characters in systems like Chinese; or the number of Emojis available on your phone. Consider also times when you want to include characters from multiple languages in a single document. Other standards, like Unicode, exist to more fully represent all characters. There are standard ways to represent these larger alphabets using ASCII characters.

Bases

Consider binary, decimal, and hexadecimal numbers. Binary is Base2 — each character can be either a '0' or a '1'. The word 'hello' represented in binary is '01101000 01100101 01101100 01101100 01101111', with eight characters representing one of 256 possible ASCII characters.

Decimal is Base10, the counting system you are most familiar with — it uses the numbers 0 through 9 to represent 10 possible values of each character. In Base10 'hello' is represented as '448378203247'.

Hexadecimal is Base16. Typically the numbers 0 through 9 and the letters A through F are used to represent 16 possible values. Even though there are letters used to represent this system they aren't they same as the encoded letters ('A' encoded to ASCII and displayed as a hexadecimal number is '41')

Base64 uses 64 different characters to represent this same content. These characters are most often the letters 'A–Z', 'a–z', '0–9', '+', and '/' (the symbol '=' is used as padding also), though different standards exist. These characters were picked because they exist in ASCII, and can easily be encoded and shared across systems with little risk of intermediaries inadvertently misconverting the data.

Characters typically used to represent units in Base64
Index	Char	Index	Char	Index	Char	Index	Char
0	A	16	Q	32	g	48	w
1	B	17	R	33	h	49	x
2	C	18	S	34	i	50	y
3	D	19	T	35	j	51	z
4	E	20	U	36	k	52	0
5	F	21	V	37	l	53	1
6	G	22	W	38	m	54	2
7	H	23	X	39	n	55	3
8	I	24	Y	40	o	56	4
9	J	25	Z	41	p	57	5
10	K	26	a	42	q	58	6
11	L	27	b	43	r	59	7
12	M	28	c	44	s	60	8
13	N	29	d	45	t	61	9
14	O	30	e	46	u	62	+
15	P	31	f	47	v	63	/	(padding)	=

Base64 will often be used to represent data meant for computers to read, like binary content of images, where if a system converted the raw contents the original data would become hard to interpret.

Format

When using 64 characters of Base64 to represent EASCII, more than one digit must be used to record one of the 256 possible characters.

In Base2, 256 characters can be represented in 8 digits, or 8 'bits'. For example, the ASCII character 'A' in Base10 is '65', and 65 in Base2 is '01000001'. Base64 can represent 6 bits of information, so 2 digits are used to record more than that: 'A''s index 65 is encoded as 'QQ' in Base64, using 12 bits of information.

Since only 8 of 12 bits are used to represent a character, the remaining 4 can be used to represent part of another character. In total, 4 characters of Base64 are equal to 3 EASCII characters.

Format  |
text    | h        e        l        l        o
binary  | 01101000 01100101 01101100 01101100 01101111 
        |    v (split in to 6 bit chunks)
        | 011010 000110 010101 101100 011011 000110 1111(00)
base10 | 26     6      21     44     27     6      60
base64 | a      G      V      s      b      G      8
output  | aGVsbG8=

Colophon

The default typeface is Overpass Mono. It is open-source, released in 2015. The Overpass series is based on Highway Gothic, a sans-serif series developed by the United States Highway Administration, originally specified in 1948, prepared with an eye towards keeping street signs legible at high speeds and in suboptimal lighting or atmospheric conditions.

Encode and Decode Base64