QR Code Encoding Formats — UTF-8, Kanji, Numeric, and Binary Modes

QR codes support four encoding modes, each optimized for different types of data. The mode determines how efficiently data is stored and how many characters you can fit into a single code. Understanding this helps you create smaller, more scannable QR codes.

The Four Encoding Modes

Mode	Characters Supported	Bits per Character	Max Capacity
Numeric	0-9	3.33	7,089 digits
Alphanumeric	0-9, A-Z, space, $%*+-./:	5.5	4,296 characters
Byte (UTF-8)	Any byte value (full Unicode)	8	2,953 bytes
Kanji	Shift JIS double-byte characters	13	1,817 characters

Most QR generators, including QRMax, automatically select the most efficient mode based on your input data.

How Mode Selection Works

The encoder scans your data and picks the most compact mode:

• "12345" → Numeric mode (most compact: 3.33 bits per digit)
• "HELLO WORLD" → Alphanumeric mode (only uppercase, limited symbols)
• "hello world" → Byte mode (lowercase forces byte mode)
• "https://example.com" → Byte mode (lowercase letters and special characters)
• Japanese text → Kanji mode (if using Shift JIS encoding)

Important: Alphanumeric mode only supports uppercase letters. A URL with lowercase letters (which is almost all URLs) uses Byte mode, consuming more space per character.

Mixed-Mode Encoding

A single QR code can switch between modes mid-stream. For example, a code containing PRODUCT-001: $29.99 might use:

1. Alphanumeric mode for PRODUCT-001: $
2. Numeric mode for 2999

Each mode switch adds a small overhead (mode indicator + character count), so switching only saves space when the segment is long enough to justify the overhead.

Practical Capacity by Content Type

Content	Typical Length	QR Version	Modules
Short URL	30-50 chars	3 (29x29)	841
Long URL with UTM	80-150 chars	6-8 (41-49x)	1,681-2,401
vCard (basic)	150-300 chars	7-10 (45-57x)	2,025-3,249
vCard (full)	400-600 chars	12-15 (65-77x)	4,225-5,929
WiFi credentials	50-100 chars	4-6 (33-41x)	1,089-1,681
Plain text paragraph	200-500 chars	8-13 (49-69x)	2,401-4,761

This is exactly why dynamic QR codes are smaller — they encode a short redirect URL (~25 chars) instead of the full destination.

ECI (Extended Channel Interpretation)

For non-Latin scripts beyond Kanji (Arabic, Cyrillic, Chinese, etc.), QR codes use ECI mode with a byte-mode payload. The ECI indicator tells the scanner which character encoding to use (UTF-8, ISO-8859-1, etc.).

Most modern scanners default to UTF-8 interpretation for byte-mode data, which handles virtually all languages correctly.

Version and Size

QR codes have 40 versions (1 through 40). Version 1 is 21x21 modules, and each subsequent version adds 4 modules per side. Version 40 is 177x177 modules — the maximum.

Higher data capacity means higher versions, which means more modules, which means larger codes for reliable scanning. The practical sweet spot is versions 2-10 for most use cases.

Does URL shortening help reduce QR code size?

Yes. A short URL like qrmax.io/r/abc encodes more compactly than yourwebsite.com/products/category/very-long-product-name?utm_source=brochure. Dynamic QR codes from QRMax use short redirect URLs by default.

Can QR codes store images or files?

Technically yes (as binary data in byte mode), but the capacity is too small for practical use. A QR code maxes out at about 3 KB of binary data — enough for a few sentences, not an image. Use a URL that links to the file instead.

Why does my QR code look so dense?

Dense codes mean lots of data. Shorten your content, switch to a dynamic QR code with a short redirect URL, or reduce the error correction level from H to M.

Related Articles

• QR Code Error Correction Explained — error correction impacts capacity
• Dynamic vs Static QR Codes — why dynamic codes are smaller
• QR Code vs Barcode — 1D vs 2D encoding differences