Why is é two bytes of hex and not one?

Because the text is encoded as UTF-8, which is what files, web pages, databases and network connections actually hold. In UTF-8 the first 128 characters take one byte each and everything else takes two, three or four, so é is c3 a9. A converter that shows e9 for é is using Latin-1, one byte per character, which is a different thing and will not match the bytes in your file. The byte count next to the result is there so the difference is visible.

What does "an odd number of hex digits" mean?

Every byte is exactly two hex digits, so a valid string of hex has an even number of them. An odd count means one digit is missing or one is extra, usually from a copy that clipped the end. Nothing is padded with a zero or trimmed to fit here, because either guess would hand you a byte you never had: the conversion stops and says how many digits it counted.

Does it accept hex with 0x prefixes, commas or colons?

Yes. Hex going in can be separated by spaces, commas, colons, semicolons, hyphens, underscores or line breaks, can carry an 0x or a backslash x in front of each byte, and can run together with nothing between the bytes at all. Mixed forms work too. Anything that is not a hex digit or a separator is named with its position instead of being skipped. On the way out you choose the separator and whether the digits are lower case or upper case.

What happens if the hex is not valid UTF-8?

It is refused, with the byte, its position and the rule it breaks. A continuation byte with nothing to continue, a sequence that stops in the middle of a character, a value written the long way round, a surrogate half and a value above U+10FFFF each get their own message. Most tools hand back U+FFFD in place of the bad byte, which looks like a successful conversion of text you never had, so this one stops instead.

How much can I convert, and does anything leave my computer?

Up to 1,000,000 characters in one pass, which is the point past which rebuilding the output on every keystroke stops feeling like typing. Past it the input is refused with its own size quoted and nothing is cut off. The conversion is arithmetic that runs in your browser: nothing is uploaded, there is no account, and up to 100,000 characters of what you type is kept in this browser alone so it is still there when you come back. The Start over button forgets it.

How do I convert hex to text or decode a compact hex string?

Swap direction to read hex and write text, or open Hex to Text. 4869, 48 69 and 0x48 0x69 each decode to Hi. Whitespace and recognized separators separate bytes; arbitrary characters, incomplete hex pairs and invalid UTF-8 are refused.

Can I look up ASCII characters, controls and hexadecimal codes?

ASCII to Hex includes the complete 0 to 127 ASCII table, with decimal, hexadecimal and binary byte values. 41 is A, 20 is a space, 0A is a line feed and 0D is a carriage return. Controls may look blank when decoded; the table names them. A0 is not an ASCII byte: a non-breaking space in UTF-8 is C2 A0.

Is this the same as hex to decimal, a hex dump editor or Unicode code-point conversion?

This tool converts text bytes. Number Base Converter converts an integer such as FF to 255. Unicode Character Picker looks up code points. This page does not parse hex dumps with offset or ASCII columns, edit binary files, process packet captures, infer UTF-16 or legacy encodings, generate decryption keys, or provide code in a programming language.

Do preset pages replace my remembered settings?

Only choices you explicitly change are saved. An ASCII or decoding preset does not overwrite a remembered separator, letter case or other mode. Drafts record their own direction so a hex draft is not silently restored as ordinary text on a different preset.

ASCII to Hex

Convert ASCII characters and hexadecimal bytes, with a complete ASCII code table below. This page starts in ASCII only mode and refuses characters or bytes outside 0 to 127. Swap direction to decode hex as ASCII. Controls such as 00, 0A and 0D are real characters that may look blank; the table names them.

TextASCII only

Hex12 bytes

48 65 6c 6c 6f 2c 20 77 6f 72 6c 64

Bytes

Encoding

Separator

Case

Hex ready. 12 bytes from 12 characters. ASCII, lower case, separated by a space.

12 bytes from 12 characters. ASCII, lower case, separated by a space.

Hello, worldUTF-8
48 65 6c 6c 6f 2c 20 77 6f 72 6c 64
Emojione 4-byte code point
“😀” (U+1F600) at character 1 is outside ASCII, which covers only the first 128 characters. Switch the encoding to UTF-8 to convert it, where it becomes 4 bytes.
Odd-length hex indecode
That is 3 hex digits, an odd number. Every byte is two digits, so one digit is missing or one is extra: check the end of what you pasted.

What the bytes are. Text on both sides of this page is UTF-8: the encoding the web, and almost every file and database written this century, uses. One character is one byte only for the first 128 characters, the ones ASCII covers. An accent is two bytes, most CJK characters are three, and an emoji is four, which is why the byte count sits next to the result rather than being left for you to work out. ASCII only is the same encoder with a refusal attached: anything that would take more than one byte stops the conversion and says which character it was, instead of being widened without telling you. Hex coming in is read the same way whatever the separator setting says, so spaces, commas, colons, hyphens and 0x prefixes all work, and a byte that is not valid UTF-8 is named with its position rather than turned into a replacement character.

Up to 1,000,000 characters in one pass, converted here in your browser with nothing uploaded. Up to 100,000 characters of what you type is kept in this browser alone so it is still here when you come back, and the Start over button above forgets it.

Accuracy. Exact byte-for-byte conversion. Text is encoded as UTF-8 before it is shown as hex, so a character outside ASCII becomes more than one byte, and the byte count says so.

Complete ASCII to hexadecimal and binary table

ASCII has 128 values, from 0 through 127. Control abbreviations name non-printing characters; this table does not include extended ASCII or a legacy code page.

Decimal	Hex	Binary byte	Character
0	00	00000000	NUL
1	01	00000001	SOH
2	02	00000010	STX
3	03	00000011	ETX
4	04	00000100	EOT
5	05	00000101	ENQ
6	06	00000110	ACK
7	07	00000111	BEL
8	08	00001000	BS
9	09	00001001	HT
10	0A	00001010	LF
11	0B	00001011	VT
12	0C	00001100	FF
13	0D	00001101	CR
14	0E	00001110	SO
15	0F	00001111	SI
16	10	00010000	DLE
17	11	00010001	DC1
18	12	00010010	DC2
19	13	00010011	DC3
20	14	00010100	DC4
21	15	00010101	NAK
22	16	00010110	SYN
23	17	00010111	ETB
24	18	00011000	CAN
25	19	00011001	EM
26	1A	00011010	SUB
27	1B	00011011	ESC
28	1C	00011100	FS
29	1D	00011101	GS
30	1E	00011110	RS
31	1F	00011111	US
32	20	00100000	Space
33	21	00100001	!
34	22	00100010	"
35	23	00100011	#
36	24	00100100	$
37	25	00100101	%
38	26	00100110	&
39	27	00100111	'
40	28	00101000	(
41	29	00101001	)
42	2A	00101010	*
43	2B	00101011	+
44	2C	00101100	,
45	2D	00101101	-
46	2E	00101110	.
47	2F	00101111	/
48	30	00110000	0
49	31	00110001	1
50	32	00110010	2
51	33	00110011	3
52	34	00110100	4
53	35	00110101	5
54	36	00110110	6
55	37	00110111	7
56	38	00111000	8
57	39	00111001	9
58	3A	00111010	:
59	3B	00111011	;
60	3C	00111100	<
61	3D	00111101	=
62	3E	00111110	>
63	3F	00111111	?
64	40	01000000	@
65	41	01000001	A
66	42	01000010	B
67	43	01000011	C
68	44	01000100	D
69	45	01000101	E
70	46	01000110	F
71	47	01000111	G
72	48	01001000	H
73	49	01001001	I
74	4A	01001010	J
75	4B	01001011	K
76	4C	01001100	L
77	4D	01001101	M
78	4E	01001110	N
79	4F	01001111	O
80	50	01010000	P
81	51	01010001	Q
82	52	01010010	R
83	53	01010011	S
84	54	01010100	T
85	55	01010101	U
86	56	01010110	V
87	57	01010111	W
88	58	01011000	X
89	59	01011001	Y
90	5A	01011010	Z
91	5B	01011011	[
92	5C	01011100	\
93	5D	01011101	]
94	5E	01011110	^
95	5F	01011111	_
96	60	01100000	`
97	61	01100001	a
98	62	01100010	b
99	63	01100011	c
100	64	01100100	d
101	65	01100101	e
102	66	01100110	f
103	67	01100111	g
104	68	01101000	h
105	69	01101001	i
106	6A	01101010	j
107	6B	01101011	k
108	6C	01101100	l
109	6D	01101101	m
110	6E	01101110	n
111	6F	01101111	o
112	70	01110000	p
113	71	01110001	q
114	72	01110010	r
115	73	01110011	s
116	74	01110100	t
117	75	01110101	u
118	76	01110110	v
119	77	01110111	w
120	78	01111000	x
121	79	01111001	y
122	7A	01111010	z
123	7B	01111011	{
124	7C	01111100	\|
125	7D	01111101	}
126	7E	01111110	~
127	7F	01111111	DEL

Common questions

Why is é two bytes of hex and not one?: Because the text is encoded as UTF-8, which is what files, web pages, databases and network connections actually hold. In UTF-8 the first 128 characters take one byte each and everything else takes two, three or four, so é is c3 a9. A converter that shows e9 for é is using Latin-1, one byte per character, which is a different thing and will not match the bytes in your file. The byte count next to the result is there so the difference is visible.
What does "an odd number of hex digits" mean?: Every byte is exactly two hex digits, so a valid string of hex has an even number of them. An odd count means one digit is missing or one is extra, usually from a copy that clipped the end. Nothing is padded with a zero or trimmed to fit here, because either guess would hand you a byte you never had: the conversion stops and says how many digits it counted.
Does it accept hex with 0x prefixes, commas or colons?: Yes. Hex going in can be separated by spaces, commas, colons, semicolons, hyphens, underscores or line breaks, can carry an 0x or a backslash x in front of each byte, and can run together with nothing between the bytes at all. Mixed forms work too. Anything that is not a hex digit or a separator is named with its position instead of being skipped. On the way out you choose the separator and whether the digits are lower case or upper case.
What happens if the hex is not valid UTF-8?: It is refused, with the byte, its position and the rule it breaks. A continuation byte with nothing to continue, a sequence that stops in the middle of a character, a value written the long way round, a surrogate half and a value above U+10FFFF each get their own message. Most tools hand back U+FFFD in place of the bad byte, which looks like a successful conversion of text you never had, so this one stops instead.
What is ASCII only mode for?: It is the same encoder with a refusal attached, for when you need to know the text is plain. In ASCII only mode any character that would take more than one byte stops the conversion and is named, and any byte above 0x7f in hex you paste is refused the same way. Switch the encoding back to UTF-8 and the same input converts.
How much can I convert, and does anything leave my computer?: Up to 1,000,000 characters in one pass, which is the point past which rebuilding the output on every keystroke stops feeling like typing. Past it the input is refused with its own size quoted and nothing is cut off. The conversion is arithmetic that runs in your browser: nothing is uploaded, there is no account, and up to 100,000 characters of what you type is kept in this browser alone so it is still there when you come back. The Start over button forgets it.
How do I convert hex to text or decode a compact hex string?: Swap direction to read hex and write text, or open Hex to Text. 4869, 48 69 and 0x48 0x69 each decode to Hi. Whitespace and recognized separators separate bytes; arbitrary characters, incomplete hex pairs and invalid UTF-8 are refused.
Can I look up ASCII characters, controls and hexadecimal codes?: ASCII to Hex includes the complete 0 to 127 ASCII table, with decimal, hexadecimal and binary byte values. 41 is A, 20 is a space, 0A is a line feed and 0D is a carriage return. Controls may look blank when decoded; the table names them. A0 is not an ASCII byte: a non-breaking space in UTF-8 is C2 A0.
Is this the same as hex to decimal, a hex dump editor or Unicode code-point conversion?: This tool converts text bytes. Number Base Converter converts an integer such as FF to 255. Unicode Character Picker looks up code points. This page does not parse hex dumps with offset or ASCII columns, edit binary files, process packet captures, infer UTF-16 or legacy encodings, generate decryption keys, or provide code in a programming language.
Do preset pages replace my remembered settings?: Only choices you explicitly change are saved. An ASCII or decoding preset does not overwrite a remembered separator, letter case or other mode. Drafts record their own direction so a hex draft is not silently restored as ordinary text on a different preset.

Exact byte-for-byte conversion. Text is encoded as UTF-8 before it is shown as hex, so a character outside ASCII becomes more than one byte, and the byte count says so.