I’ve compiled useful links regarding QR code specifications and creation services.

QR Code 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

About QR Code Specifications

・FAQ｜QRコードドットコム｜株式会社デンソーウェーブ

・QRコード作成 for ビジネス：FAQ

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.