Encoding Mode

Encoding mode is the method used to convert data into QR code module patterns. Four types exist: numeric (0-9 only), alphanumeric (0-9, A-Z, some symbols), byte (arbitrary binary data), and kanji (Shift JIS kanji characters).

Numeric mode consumes the fewest bits per character, storing more data in the same QR code size. QR code generators typically auto-select the most efficient mode for the input data. URLs are encoded in alphanumeric mode, making them more space-efficient than Japanese text.

Which mode was used to encode the data is signaled by a 4-bit mode indicator placed at the start of the data stream. Numeric mode is 0001, alphanumeric mode is 0010, byte mode is 0100, and kanji mode is 1000. The reader inspects these four bits to decide how to interpret the data that follows.