Common Hex Values - Printable ASCII, Control Codes & Color Reference

How to Use This Page

This page is a working reference for the hex values you actually use day to day: the printable ASCII set, the most common control codes, the URL-encoding table, and the file signatures that show up in hex dumps. It is intentionally not exhaustive — for that, the official Unicode code charts and the IANA registry of file signatures are linked at the bottom. Everything here is the subset we reach for ourselves.

If you find yourself coming back to this page more than once a week, the tables below are small enough to internalise entirely. After that, you will not need to look anything up.

Printable ASCII (0x20–0x7E)

Printable ASCII covers 95 characters: space, the punctuation characters, the digits 0–9, the uppercase alphabet, and the lowercase alphabet. Every character in this range fits in a single byte, and the high bit is zero.

Char	Dec	Hex	Char	Dec	Hex	Char	Dec	Hex	Char	Dec	Hex
(sp)	32	20	0	48	30	@	64	40	P	80	50
!	33	21	1	49	31	A	65	41	Q	81	51
"	34	22	2	50	32	B	66	42	R	82	52
#	35	23	3	51	33	C	67	43	S	83	53
$	36	24	4	52	34	D	68	44	T	84	54
%	37	25	5	53	35	E	69	45	U	85	55
&	38	26	6	54	36	F	70	46	V	86	56
'	39	27	7	55	37	G	71	47	W	87	57
(	40	28	8	56	38	H	72	48	X	88	58
)	41	29	9	57	39	I	73	49	Y	89	59
*	42	2A	:	58	3A	J	74	4A	Z	90	5A
+	43	2B	;	59	3B	K	75	4B	[	91	5B
,	44	2C	<	60	3C	L	76	4C	\	92	5C
-	45	2D	=	61	3D	M	77	4D	]	93	5D
.	46	2E	>	62	3E	N	78	4E	^	94	5E
/	47	2F	?	63	3F	O	79	4F	_	95	5F
									`	96	60
									a	97	61
									b	98	62
									c	99	63
									d	100	64
									e	101	65
									f	102	66
									g	103	67
									h	104	68
									i	105	69
									j	106	6A
									k	107	6B
									l	108	6C
									m	109	6D
									n	110	6E
									o	111	6F
									p	112	70
									q	113	71
									r	114	72
									s	115	73
									t	116	74
									u	117	75
									v	118	76
									w	119	77
									x	120	78
									y	121	79
									z	122	7A
									{	123	7B
									\|	124	7C
									}	125	7D
									~	126	7E

The remaining printable codes, 0x7F (delete) and everything below 0x20, are control characters. They are not printable, but they show up constantly in network protocols, log files, and binary formats.

Common Control Codes (0x00–0x1F)

The first 32 ASCII codes are non-printable control characters. They were originally defined for controlling teleprinters, but a handful of them are still in active use today.

Hex	Dec	Name	Where it shows up
00	0	NUL	C string terminator, null bytes in binary protocols
01	1	SOH	Start of heading, very rare outside legacy protocols
02	2	STX	Start of text, used in some serial protocols
03	3	ETX	End of text, Ctrl+C, common in framing protocols
04	4	EOT	End of transmission
05	5	ENQ	Enquiry, very rare
06	6	ACK	Acknowledgement, used in serial comms and TLS
07	7	BEL	Terminal bell, system beep
08	8	BS	Backspace, also used in regex word boundaries
09	9	HT (TAB)	Horizontal tab, \t in most languages
0A	10	LF	Line feed, \n in Unix, second byte in Windows CRLF
0B	11	VT	Vertical tab, rare
0C	12	FF	Form feed, page break in printer output
0D	13	CR	Carriage return, \r, first byte in Windows CRLF
1B	27	ESC	Escape, first byte of ANSI terminal control sequences

Two of these — 0x0A (LF) and 0x0D (CR) — are responsible for almost every "weird newline" bug you have ever seen. Unix uses LF only, classic Mac used CR only, and Windows uses CRLF (the pair 0x0D 0x0A). Most modern tools handle all three, but the bytes still show up in hex dumps and are worth recognising on sight.

File Signatures (Magic Numbers)

The first few bytes of a file identify its type. When you see an unfamiliar file in a hex dump, the magic number is almost always the fastest way to figure out what it is. The table below lists the magic numbers for the formats you are most likely to encounter on the modern web.

File type	First bytes (hex)	ASCII shown
PNG image	89 50 4E 47 0D 0A 1A 0A	‹PNG›
JPEG image	FF D8 FF	(binary)
GIF image	47 49 46 38	GIF8
PDF document	25 50 44 46 2D	%PDF-
ZIP archive	50 4B 03 04	PK..
GZIP archive	1F 8B	(binary)
tar archive	75 73 74 61 72	ustar
ELF executable (Linux)	7F 45 4C 46	.ELF
Mach-O executable (macOS)	CF FA ED FE	(binary)
PE executable (Windows)	4D 5A	MZ
WebP image	52 49 46 46 ?? ?? ?? ?? 57 45 42 50	RIFF....WEBP
MP4 / MOV video	00 00 00 ?? 66 74 79 70	....ftyp
UTF-8 BOM	EF BB BF	(binary)
UTF-16 LE BOM	FF FE	(binary)

For the authoritative, comprehensive list, the IANA registry of media types and the file command's magic database (typically /usr/share/file/magic on Linux) are the canonical sources.

Common URL-Encoded Characters

URLs may only safely contain a subset of ASCII. Characters outside that set are percent-encoded, where the percent is followed by two hex digits giving the character's code point. The most common URL-encoded characters are shown below.

Character	Hex	URL-encoded	When you see it
(space)	20	%20	Spaces in query strings, often + in form data
!	21	%21	Rare; usually safe in URLs
"	22	%22	Double quotes inside query values
#	23	%23	Hash literal, must be encoded in query values
%	25	%25	Literal percent sign
&	26	%26	Ampersand in query values
'	27	%27	Single quote
+	2B	%2B	Plus sign, ambiguous in form-encoded data
/	2F	%2F	Slash in path components
:	3A	%3A	Colon in path segments
=	3D	%3D	Equals in query values
?	3F	%3F	Question mark, separates path from query
@	40	%40	At sign in user info
<	3C	%3C	Less-than
>	3E	%3E	Greater-than
\	5C	%5C	Backslash, used in Windows paths
\|	7C	%7C	Pipe, sometimes seen in URLs

A quick way to recognise percent-encoding in the wild: any time you see a % followed by two characters in the ranges 0–9, A–F, or a–f, that is a percent-encoded byte. Decode it by treating the two characters as a hex number.

Common CSS Colour Hex Codes

A short reference of the most-used CSS named colours and their hex equivalents. The full list of 147 named CSS colours is in the CSS Color Module Level 4 spec, linked at the bottom.

Name	Hex	RGB
black	#000000	0, 0, 0
white	#FFFFFF	255, 255, 255
red	#FF0000	255, 0, 0
lime	#00FF00	0, 255, 0
blue	#0000FF	0, 0, 255
yellow	#FFFF00	255, 255, 0
cyan / aqua	#00FFFF	0, 255, 255
magenta / fuchsia	#FF00FF	255, 0, 255
silver	#C0C0C0	192, 192, 192
gray	#808080	128, 128, 128
maroon	#800000	128, 0, 0
olive	#808000	128, 128, 0
green	#008000	0, 128, 0
purple	#800080	128, 0, 128
teal	#008080	0, 128, 128
navy	#000080	0, 0, 128
orange	#FFA500	255, 165, 0

For a deeper treatment of how hex colours are constructed and how to design accessible palettes around them, see the dedicated hex colours guide.

Reserved and Special Values

A handful of hex values come up so often in special contexts that they are worth knowing by themselves.

0x00 — the null byte. Marks the end of a C string and is a frequent source of bugs in fixed-width buffers (truncation at the first null, missing data after a null in a foreign format).
0x0A and 0x0D — LF and CR, the line-ending bytes. See the control codes table above.
0xFF — "all bits set" in an 8-bit value. Used as a sentinel value, a max sentinel, and a mask for the low byte of a 16-bit word.
0xFFFF, 0xFFFFFFFF — all bits set in 16 and 32 bits respectively. The "broadcast" address in IPv4 (255.255.255.255) is the decimal form of 0xFFFFFFFF.
0x7F — the delete control code, and also the high bit of a 7-bit ASCII value.
0x80, 0x8000, 0x80000000 — the sign bit set in 8, 16, and 32 bits. The smallest negative number in two's-complement signed types.
0xDEADBEEF, 0xCAFEBABE — sentinels used to mark uninitialised or special memory regions in many codebases. Recognise them on sight.

External References

When this page is not enough — and it eventually will not be, because hex shows up in every domain — these are the resources we reach for:

Unicode code charts — the authoritative reference for every code point, including the full hex range above 0x7F.
CSS Color Module Level 4 — the formal definition of every CSS named colour, including the 148 named colours in the basic and extended sets.
RFC 4648 — the canonical spec for base16 (hex), base32, and base64 encoding.
RFC 3986 — the URL syntax spec, which defines percent-encoding (Section 2.1) and the unreserved character set (Section 2.3).
The file command's magic database (typically /usr/share/file/magic on Linux) — the comprehensive list of file signatures and their interpretations.