Why does an emoji count as 2 in JavaScript?

JavaScript string length counts UTF-16 code units. Many emoji are one Unicode code point represented by a surrogate pair, so they take two UTF-16 code units.

Why do two strings look identical but compare differently?

They may use different Unicode sequences, such as a precomposed character versus a base letter plus combining mark, or a normal space versus a non-breaking space.

Why is UTF-8 unavailable for some pasted text?

The text may contain ill-formed UTF-16 such as a lone surrogate. JavaScript can hold that raw data, but valid UTF-8 requires Unicode scalar values.

Why is a code point valid even if it renders as a box or tofu?

Unicode validity and device font support are different things. A valid code point can still lack a glyph on the current system.

Why doesn't Toolzy show an official name for every assigned character yet?

This v1 ships with a pinned local name subset for ASCII and common debugging characters so the tool stays lightweight. Status detection still works for all code points without runtime fetches.

ASCII / Unicode Explorer

Inspect pasted text, Unicode code points, UTF-8 bytes, UTF-16 code units, JavaScript escapes, and a full 128-row ASCII table without leaving the browser.

Raw text input

UTF-16 code units

Unicode code points

UTF-8 bytes

Grapheme clusters

Lines

CRLF 0 · CR 0 · LF 1

Surrogate-pair sequence detected

At least one selected symbol uses two UTF-16 code units for one Unicode code point. This is why JavaScript string length can be larger than the visible symbol count.

Combining-mark sequence detected

A combining mark modifies the character before it instead of standing alone. One visible glyph can therefore span multiple code points even when the text looks like a single character.

Normalization difference detected

The original text changes under NFC normalization, so visually identical strings may compare differently until they are normalized to the same canonical form.

Selected code point

Assigned Unicode code point (name not included in pinned v1 dataset)

U+0041 · valid Unicode scalar value

ASCIIprintable

ASCII subset

This value is inside the 7-bit ASCII range U+0000 through U+007F, so it is valid ASCII as well as Unicode.

Toolzy is still loading the official Unicode name for this assigned code point from the local chunked dataset.

ASCII subset

Literal

U+ notation

U+0041

Hex

0x41

Decimal

Binary

1000001

UTF-8 bytes

0x41

UTF-16 code units

0x0041

JS escape

\u0041

JS code point escape

\u{41}

HTML numeric reference (decimal)

HTML numeric reference (hex)

Code point breakdown

One row per Unicode code point, not one row per UTF-16 index.

#	Preview	Name / status	U+	Dec	UTF-16	UTF-8	Labels
1	A	Assigned Unicode code point (name not included in pinned v1 dataset) A	U+0041	65	0x0041	0x41	ASCIIprintable
2	TAB	CHARACTER TABULATION TAB	U+0009	9	0x0009	0x09	ASCIIcontrol
3	C	Assigned Unicode code point (name not included in pinned v1 dataset) C	U+0043	67	0x0043	0x43	ASCIIprintable
4	a	Assigned Unicode code point (name not included in pinned v1 dataset) a	U+0061	97	0x0061	0x61	ASCIIprintable
5	f	Assigned Unicode code point (name not included in pinned v1 dataset) f	U+0066	102	0x0066	0x66	ASCIIprintable
6	e	Assigned Unicode code point (name not included in pinned v1 dataset) e	U+0065	101	0x0065	0x65	ASCIIprintable
7	COMBINING ACUTE	COMBINING ACUTE ACCENT ́	U+0301	769	0x0301	0xCC 0x81	printablecombining mark
8	LF	LINE FEED LF	U+000A	10	0x000A	0x0A	ASCIIcontrol
9	ZWSP	ZERO WIDTH SPACE ZWSP	U+200B	8203	0x200B	0xE2 0x80 0x8B	invisible
10	😀	Assigned Unicode code point (name not included in pinned v1 dataset) 😀	U+01F600	128512	0xD83D 0xDE00	0xF0 0x9F 0x98 0x80	printable

ASCII is exactly 128 values. Rows 0x80-0xFF are not ASCII.

Dec	Hex	Binary	Abbr	Name	Preview
0	0x00	00000000	NUL	NULL	NUL
1	0x01	00000001	SOH	START OF HEADING	SOH
2	0x02	00000010	STX	START OF TEXT	STX
3	0x03	00000011	ETX	END OF TEXT	ETX
4	0x04	00000100	EOT	END OF TRANSMISSION	EOT
5	0x05	00000101	ENQ	ENQUIRY	ENQ
6	0x06	00000110	ACK	ACKNOWLEDGE	ACK
7	0x07	00000111	BEL	BELL	BEL
8	0x08	00001000	BS	BACKSPACE	BS
9	0x09	00001001	TAB	CHARACTER TABULATION	TAB
10	0x0A	00001010	LF	LINE FEED	LF
11	0x0B	00001011	VT	LINE TABULATION	VT
12	0x0C	00001100	FF	FORM FEED	FF
13	0x0D	00001101	CR	CARRIAGE RETURN	CR
14	0x0E	00001110	SO	SHIFT OUT	SO
15	0x0F	00001111	SI	SHIFT IN	SI
16	0x10	00010000	DLE	DATA LINK ESCAPE	DLE
17	0x11	00010001	DC1	DEVICE CONTROL ONE	DC1
18	0x12	00010010	DC2	DEVICE CONTROL TWO	DC2
19	0x13	00010011	DC3	DEVICE CONTROL THREE	DC3
20	0x14	00010100	DC4	DEVICE CONTROL FOUR	DC4
21	0x15	00010101	NAK	NEGATIVE ACKNOWLEDGE	NAK
22	0x16	00010110	SYN	SYNCHRONOUS IDLE	SYN
23	0x17	00010111	ETB	END OF TRANSMISSION BLOCK	ETB
24	0x18	00011000	CAN	CANCEL	CAN
25	0x19	00011001	EM	END OF MEDIUM	EM
26	0x1A	00011010	SUB	SUBSTITUTE	SUB
27	0x1B	00011011	ESC	ESCAPE	ESC
28	0x1C	00011100	FS	FILE SEPARATOR	FS
29	0x1D	00011101	GS	GROUP SEPARATOR	GS
30	0x1E	00011110	RS	RECORD SEPARATOR	RS
31	0x1F	00011111	US	UNIT SEPARATOR	US
32	0x20	00100000		ASCII value
33	0x21	00100001	!	ASCII value	!
34	0x22	00100010	"	ASCII value	"
35	0x23	00100011	#	ASCII value	#
36	0x24	00100100	$	ASCII value	$
37	0x25	00100101	%	ASCII value	%
38	0x26	00100110	&	ASCII value	&
39	0x27	00100111	'	ASCII value	'
40	0x28	00101000	(	ASCII value	(
41	0x29	00101001	)	ASCII value	)
42	0x2A	00101010	*	ASCII value	*
43	0x2B	00101011	+	ASCII value	+
44	0x2C	00101100	,	ASCII value	,
45	0x2D	00101101	-	ASCII value	-
46	0x2E	00101110	.	ASCII value	.
47	0x2F	00101111	/	ASCII value	/
48	0x30	00110000	0	ASCII value	0
49	0x31	00110001	1	ASCII value	1
50	0x32	00110010	2	ASCII value	2
51	0x33	00110011	3	ASCII value	3
52	0x34	00110100	4	ASCII value	4
53	0x35	00110101	5	ASCII value	5
54	0x36	00110110	6	ASCII value	6
55	0x37	00110111	7	ASCII value	7
56	0x38	00111000	8	ASCII value	8
57	0x39	00111001	9	ASCII value	9
58	0x3A	00111010	:	ASCII value	:
59	0x3B	00111011	;	ASCII value	;
60	0x3C	00111100	<	ASCII value	<
61	0x3D	00111101	=	ASCII value	=
62	0x3E	00111110	>	ASCII value	>
63	0x3F	00111111	?	ASCII value	?
64	0x40	01000000	@	ASCII value	@
65	0x41	01000001	A	ASCII value	A
66	0x42	01000010	B	ASCII value	B
67	0x43	01000011	C	ASCII value	C
68	0x44	01000100	D	ASCII value	D
69	0x45	01000101	E	ASCII value	E
70	0x46	01000110	F	ASCII value	F
71	0x47	01000111	G	ASCII value	G
72	0x48	01001000	H	ASCII value	H
73	0x49	01001001	I	ASCII value	I
74	0x4A	01001010	J	ASCII value	J
75	0x4B	01001011	K	ASCII value	K
76	0x4C	01001100	L	ASCII value	L
77	0x4D	01001101	M	ASCII value	M
78	0x4E	01001110	N	ASCII value	N
79	0x4F	01001111	O	ASCII value	O
80	0x50	01010000	P	ASCII value	P
81	0x51	01010001	Q	ASCII value	Q
82	0x52	01010010	R	ASCII value	R
83	0x53	01010011	S	ASCII value	S
84	0x54	01010100	T	ASCII value	T
85	0x55	01010101	U	ASCII value	U
86	0x56	01010110	V	ASCII value	V
87	0x57	01010111	W	ASCII value	W
88	0x58	01011000	X	ASCII value	X
89	0x59	01011001	Y	ASCII value	Y
90	0x5A	01011010	Z	ASCII value	Z
91	0x5B	01011011	[	ASCII value	[
92	0x5C	01011100	\	ASCII value	\
93	0x5D	01011101	]	ASCII value	]
94	0x5E	01011110	^	ASCII value	^
95	0x5F	01011111	_	ASCII value	_
96	0x60	01100000	`	ASCII value	`
97	0x61	01100001	a	ASCII value	a
98	0x62	01100010	b	ASCII value	b
99	0x63	01100011	c	ASCII value	c
100	0x64	01100100	d	ASCII value	d
101	0x65	01100101	e	ASCII value	e
102	0x66	01100110	f	ASCII value	f
103	0x67	01100111	g	ASCII value	g
104	0x68	01101000	h	ASCII value	h
105	0x69	01101001	i	ASCII value	i
106	0x6A	01101010	j	ASCII value	j
107	0x6B	01101011	k	ASCII value	k
108	0x6C	01101100	l	ASCII value	l
109	0x6D	01101101	m	ASCII value	m
110	0x6E	01101110	n	ASCII value	n
111	0x6F	01101111	o	ASCII value	o
112	0x70	01110000	p	ASCII value	p
113	0x71	01110001	q	ASCII value	q
114	0x72	01110010	r	ASCII value	r
115	0x73	01110011	s	ASCII value	s
116	0x74	01110100	t	ASCII value	t
117	0x75	01110101	u	ASCII value	u
118	0x76	01110110	v	ASCII value	v
119	0x77	01110111	w	ASCII value	w
120	0x78	01111000	x	ASCII value	x
121	0x79	01111001	y	ASCII value	y
122	0x7A	01111010	z	ASCII value	z
123	0x7B	01111011	{	ASCII value	{
124	0x7C	01111100	\|	ASCII value	\|
125	0x7D	01111101	}	ASCII value	}
126	0x7E	01111110	~	ASCII value	~
127	0x7F	01111111	DEL	DELETE	DEL

Unicode lookup data version: 16.0.0. This build ships a pinned local dataset of official Unicode names with no runtime fetches, while all status detection and byte calculations still run entirely in the browser.

ASCII / Unicode Explorer

Assigned Unicode code point (name not included in pinned v1 dataset)

Code point breakdown

Canonical ASCII table (0x00-0x7F)