QR character set reference: modes, values and indicators

The alphanumeric table, values 0–44

Each character has a numeric value. Characters are taken in pairs: the pair encodes as 45 × (first value) + (second value), an 11-bit number. A trailing single character takes 6 bits alone.

Value	Char	Value	Char	Value	Char
0	0	15	F	30	U
1	1	16	G	31	V
2	2	17	H	32	W
3	3	18	I	33	X
4	4	19	J	34	Y
5	5	20	K	35	Z
6	6	21	L	36	space
7	7	22	M	37	$
8	8	23	N	38	%
9	9	24	O	39	*
10	A	25	P	40	+
11	B	26	Q	41	-
12	C	27	R	42	.
13	D	28	S	43	/
14	E	29	T	44	:

Worked example: QR = 45 × 27 + 28 = 1243 = 10011011011 in 11 bits.

Note what is missing: lowercase letters, ?, =, &, #, _, ~ and @. A URL with a query string cannot stay in alphanumeric mode past the first =, which is why HTTPS://EXAMPLE.COM/ABC encodes ~31% smaller than its lowercase twin but a tracking URL gains nothing. Details in data encoding modes.

Numeric mode

Digits 0-9 only. Groups of 3 digits → 10 bits; a trailing pair takes 7 bits and a trailing single digit 4 bits. That is 3.33 bits per digit against 8 in byte mode: the reason a numeric-only payload reaches 7,089 characters while bytes stop at 2,953. One stray character (a + before a phone number, a space) disqualifies the whole segment.

Byte mode

8 bits per byte, any value. The ISO/IEC 18004 default interpretation is ISO 8859-1 (Latin-1), but near-universal practice is to store UTF-8 and rely on the decoder to detect it: every mainstream phone does. A strictly conforming encoder would announce UTF-8 with an ECI header, yet ECI itself confuses some older readers, so most generators (UseQR included) write plain UTF-8 bytes with no ECI. See UTF-8 and Unicode in QR codes.

Kanji mode

13 bits per character, for double-byte Shift-JIS characters in the ranges 0x8140–0x9FFC and 0xE040–0xEBBF. A compaction of Shift-JIS, not of Unicode: see kanji mode explained.

Mode indicators and count field widths

Every segment starts with a 4-bit mode indicator, then a character count whose width depends on the version:

Mode	Indicator	Count bits v1–9	v10–26	v27–40
Numeric	0001	10	12	14
Alphanumeric	0010	9	11	13
Byte	0100	8	16	16
Kanji	1000	8	10	12
ECI	0111	n/a	n/a	n/a
Structured append	0011	n/a	n/a	n/a
Terminator	0000	n/a	n/a	n/a

A single code may switch modes mid-stream, encoders segment the input and use the cheapest mode for each run. To see which mode a real code ended up in, decode it and read the reported mode, or start from a plain text code and vary the characters.

FAQ

What characters can a QR code contain?

Anything: byte mode stores arbitrary 8-bit data, in practice UTF-8, so all of Unicode is representable. The numeric and alphanumeric modes are optimisations for restricted character sets, not limits on what QR codes can hold.

Does a QR code support lowercase letters?

Yes, via byte mode at 8 bits per character. Only the 45-character alphanumeric set (digits, uppercase A–Z and nine symbols) qualifies for the cheaper 5.5-bit encoding.

What is the QR alphanumeric character set?

Exactly 45 characters: 0–9 (values 0–9), A–Z (10–35), space (36), then $, %, *, +, -, ., / and : (37–44). Pairs encode as 45 × first + second in 11 bits.

Why does an uppercase URL make a smaller QR code?

Uppercase letters sit in the alphanumeric set, so the segment encodes at 5.5 bits per character instead of 8. Schemes and hostnames are case-insensitive, making HTTPS://EXAMPLE.COM safe; paths are frequently case-sensitive, so leave them alone.