Darshan Sawardekar

Adds a Scroll To Top button that allows visitors to scroll back to the 
top of the page. You can customize the button style using predefined 
styles or by adding a custom CSS file in your Theme.
<h3>Credits</h3>
<ul>
<li>Thanks to <a href="http://markgoodyear.com/" rel="nofollow ugc">Mark Goodyear</a> for <a href="http://markgoodyear.com/2013/01/scrollup-jquery-plugin/" rel="nofollow ugc">scrollUp</a>.</li>
</ul>

wp-scroll-up

Adds a Button to Scroll back to Top of any Post or Page in WordPress.

Anisur Rahman

AR Back To Top plugin will help them who don’t wants to write code. For use this plugin simply download or add new plugin from WordPress plugin directory.
<h3>AR Back To Top Features</h3>
<ul>
<li>Displays a Back to Top button when the user scrolls down the page.</li>
<li>Smooth scroll animation back to the top.</li>
<li>Fully customizable — no coding required.</li>
<li>Choose from a variety of Font Awesome icons (v4.7).</li>
<li>Supports custom button size and icon size.</li>
<li>Customize button background and text color.</li>
<li>Set the button position (left or right).</li>
<li>Define scroll offset — control when the button appears.</li>
<li>Adjustable scroll duration for a smoother UX.</li>
<li>Enable or disable the button with a single click.</li>
<li>Supports custom CSS for advanced styling.</li>
<li>Show or hide the button on small devices (responsive control).</li>
<li>Option to load JavaScript asynchronously for performance.</li>
<li>Ready to use out of the box — minimal setup required.</li>
<li>Integrated settings panel in the WordPress admin area.</li>
<li>Compatible with all modern WordPress themes.</li>
<li>Cross-browser compatible (Chrome, Firefox, Safari, Edge, etc.).</li>
<li>Optimized for fast performance.</li>
</ul>

AR Back To Top

AR Back To Top is a standard WordPress plugin for back to top.

wp-scroll-up vs AR Back To Top