I’ve compiled useful links regarding QR code specifications and creation services.
You can create QR codes via Google Chart API.
・Google Chart Tools: Infographics - Infographics (Deprecated) — Google Developers
A site that can also create Micro QR Codes. It supports many output formats including PNG, PDF, SVG, EPS, SVG, etc.
・QR Code and 2D Code Generator | Kerem Erkan
In addition to QR codes, there’s also a standard called Micro QR Code. This is useful when you have few characters and want to reduce the QR code size.
・マイクロQRコード|QRコードドットコム|株式会社デンソーウェーブ
That’s all from the Gemba.