A summary of the specification is here:
* http://en.wikipedia.org/wiki/QR_code
Numeric only Max. 7,089 characters (0, 1, 2, 3, 4, 5, 6, 7, 8, 9)
Alphanumeric Max. 4,296 characters (0–9, A–Z [upper-case only], space, $, %, *, +, -, ., /, :)
Binary/byte Max. 2,953 characters (8-bit bytes) (23624 bits)
Kanji/Kana Max. 1,817 characters
The specification itself is here:
- https://www.iso.org/standard/62021.html
As far as “more space”, you should think of the QR code as a “link”, or a “shortcut” to your URL. Clicking the QR code brings the user to web site; once they’re there, you have as much space as you want.