It looks grayed because It's a right-click extension where you have 2 choices (Generate or Read), it reads QR code on website very well and even propose you to open the link on a new tab.
I did not tried on PDF, though

Anyway it works like a charm.

Simple and yet most useful QR code extension! The context-menu is quite an easy way to create QR codes.

no Useful 没用

This extresion is powerful and easy to use. Thank you!

中文乱码

Nothing happens when you try to scan a QR code.

Can only generate QR codes, can't read ANY code, even if it's generated by this very addon.

It's a trusty extension that does it's job admirably. It can both scan and generate QR codes. There no other extensions that can do both.

無法讀取QR Code

109更新后无法正常生成二维码了，希望作者能尽快修复
112.02更新后已可用，问题已解决

Нужная вещь, в две стороны. Отлично.

Works!

Не хватает автоопределения кодировки декодированного текста. Поддерживается только Unicode, Было бы неплохо добавить UTF-8, Win-1251, Win-1252, ISO-88xx, CyrMac (и все Mac-кодировки), IBM, ANSCII, KOI8-R, KOI8-U, CP-866. Спасибо.

Add the ability to delete an icon from URL BAR

Doesn't support Cyrillic Не поддерживает кириллицу

It simply works. No configuration needed at all. Intuitive.