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Zedna Ref Code Generator & Access Gate
v1.5 · by Radek Mezulanik
Generate unique code for users to allow them to access your website.
About this plugin
This plugin generates unique codes and creating custom field in user profile called Ref code.
You can enable access gate, to allow users to access website only with their unique ref code.
Access gate is just post with shortcode inside, so you can create whatever text/design you want.