WebMaestro.Fr

Upload the layers of your image, and create a parallax effect !
It works great on smart devices too !
The first step is to create with your favorite picture editing software (Photoshop, GIMP…) an independent image for each ground composing your image. All these layers shall be the same size, and should be in .png format as they are meant to include transparency areas. 
Then, on your post editing page in WordPress, click the Insert Media button, and (the same way you would create a gallery) upload your layers under the Create Parallax item. Reorganise the layers if needed, from the background to the front. 
You can finally configure the animation (calibrate, invert, limit, scalar, friction), and publish !
There is <a href="http://webmaestro.fr/image-parallax-plugin-wordpress/" rel="nofollow ugc">some examples</a> on the plugin page.
It uses <a href="http://wagerfield.github.io/parallax/" rel="nofollow ugc">parallax.js</a> by Matthew Wagerfield.

Image Parallax

Create images with a parallax effect. Upload some layers, configure the animation, and publish !

Demis Patti

Responsive website background images with a parallax effect and a user friendly interface. 
Your theme must support <a href="https://codex.wordpress.org/Custom_Backgrounds" rel="nofollow ugc">Custom Backgrounds</a>, which it most likely does already.
<h3>Features</h3>
<ul>
<li>Background image with a parallax effect</li>
<li>One image for all pages or each page individual or a mix of both, it’s all up to you</li>
<li>Serves the whole frontend</li>
<li>Works vertically and, for fun, horizontally</li>
<li>Various overlays to choose from</li>
</ul>
<h3>Requirements</h3>
<ul>
<li>Your theme must support the core WordPress implementation of the <a href="https://codex.wordpress.org/Custom_Backgrounds" rel="nofollow ugc">Custom Backgrounds</a> theme feature.</li>
<li>In order to use the parallax feature, I decided to set the minimum required image dimensions to 1920px * 1200px, which covers a fullHD screen with a slight vertical parallax movement ( Image height – viewport height, so 1200px – 1080px gives 120px offset to move the image. I hope you get the point here.).</li>
<li>You most likely need to edit some css in order to “uncover” the background image or parts of it respectively. Your theme’s layout should be “boxed”, or an opacity should be added to the page content container for the background image to be seen.</li>
<li>PHP version 8.0 or above.</li>
</ul>

cbParallax

Responsive website background images with a parallax effect and a user friendly interface. Your theme must support Custom Backgrounds, which it most l …

Image Parallax vs cbParallax