The Base32 Alphabet

Bech32 uses a custom 32-character alphabet. Like Base58, it is carefully designed to remove confusing characters, but it goes even further by eliminating all uppercase letters to optimize for modern user interfaces.

1. The Characters

The Bech32 alphabet consists of: qpzry9x8gf2tvdw0s3jn54khce6mua7l

• Lowercase Only: By using only lowercase letters (and numbers), we avoid the common "Is that a big A or a small a?" confusion.

• Excluded Characters: The characters b, i, o, and 1 (except as the separator) are completely removed.

  • 1, i, and l are often confused.
  • o, 0, and q are often confused.
  • b and 8 are often confused.

2. Why 32 characters?

The number 32 is a "Power of Two" ($2^5$). This is mathematically significant.

• In Base58, we had to use complex division because 58 isn't a power of two.

• In Base32, we can simply group bits into chunks of 5. This makes encoding and decoding incredibly fast and easy for even the simplest hardware wallets.

3. QR Code Optimization

Standard QR codes have a special "Alphanumeric Mode" that is extremely efficient.

• This mode supports uppercase letters, numbers, and a few symbols.

• Because Bech32 can be represented entirely in uppercase (as it is case-insensitive), it fits perfectly into this high-density QR mode.

• The result is a QR code that is smaller and much faster for a smartphone camera to "Lock onto."

4. The Mapping

Every character in the alphabet corresponds to a 5-bit value (0 to 31).

• q = 0

• p = 1

• z = 2

• ...and so on.

Index	Char	Index	Char
0	q	16	s
1	p	17	3
5	9	31	l

In the next section, we will discuss the HRP and Separator.