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This plugin allows you to add authentication using social media networks (Twitter, WordPress, Google+, etc.) for the users who want to comment on your blog. 
The plugin can be activated to provide authentication for all posts or only for selected posts. 
The usage of this plugin does not oblige you to create an account on our website, like others plugins do. 
All you need is to have an account (if you don’t have one, then you must create it) on the social network that you want to use as a source of authentication.
<h3>Configuration</h3>
To configure the plugin, you must follow the instructions described here: http://www.ixtendo.com/comments-with-social-login-wp-plugin/

Comments with Social Login

Add authentication using social media networks (Twitter, WordPress, Google+, etc.) for blog comments

Riyaz

GetSocial adds a lightweight and intelligent floating social media sharing box on your blog posts.
Features:
<ul>
<li>Floating social share box compatible with leading web browsers</li>
<li>Out-of-the-box functionality like
<ul>
<li>Twitter Tweet Button</li>
<li>Facebook Like and Share button</li>
<li>Google +1 Button</li>
<li>Buffer Button</li>
<li>Pinterest Button</li>
<li>LinkedIn Button</li>
<li>Stumbleupon Submit button</li>
<li>CentUp button</li>
<li>Your Own Button</li>
</ul>
</li>
<li>Easily add any number of additional social media sharing buttons</li>
<li>Re-order buttons with simple drag-and-drop</li>
<li>Hide individual share counts if desired</li>
<li>Resize GetSocial share bar width (useful for non-English blogs)</li>
<li>Always visible and accessible even if the user scrolls down the page</li>
<li>Auto-adjusts itself to all screen resolutions and window sizes</li>
<li>Automatically hides itself partially to the left of the screen if window is resized to smaller than defined width</li>
<li>Completely hides itself on tablets and mobile screens</li>
<li>Hovering over a partially hidden GetSocial box displays the full box</li>
<li>For higher screen resolutions, displays full by default</li>
<li>Easy-to-use Color Picker to customize the look and feel to match your blog theme</li>
<li>Lightweight plugin with minimal settings</li>
<li>Scripts are loaded in footer to improve page-load time</li>
</ul>
Be sure to check out: <a href="https://wordpress.org/extend/plugins/social-metrics/" title="Social Metrics Plugin" rel="ugc">Social Metrics</a> – Helps you track how your posts are shared in the social media.

GetSocial

GetSocial adds an intelligent, lightweight, quick to setup floating social media sharing box on your blog posts.

Comments with Social Login vs GetSocial