omerk

<a href="http://fancybox.net/" rel="nofollow ugc">Fancybox</a> is a tool for displaying images, html content and multi-media 
in a Mac-style “lightbox” that floats overtop of web page. It was built using the jQuery library.
This plugin inserts the necessary elements required to run Fancybox on your blog. It also groups 
images within posts using rel attributes. (Based on the code found on <a href="https://wordpress.org/support/topic/automatic-adding-lightbox-rel-and-group-to-images-in-posts" rel="ugc">this</a> 
forum thread)
To disable Fancybox per post: Add a custom field called ‘nofancybox’ and set it’s value to ‘true’. 
Instructions on how to add custom fields to posts can be found at <a href="https://codex.wordpress.org/Custom_Fields" rel="nofollow ugc">this</a> 
codex article.

Fancyboxify

This simple plugin enables Fancybox on image links. It groups all images within a single post and can also be disabled per post.

Silkalns

Seamlessly integrates FancyBox into your blog: Upload, activate, and you’re done. Additional configuration optional.
You can easily customize almost anything you can think about fancybox lightbox: the border, margin width and color, zoom speed, animation type, close button position, overlay color and opacity and even more advanced option like several options to group images into galleries, and more…
By default, the plugin will use jQuery to apply FancyBox to ANY thumbnails that link directly to an image. This includes posts, the sidebar, etc, so you can activate it and it will be applied automatically.
<h4>Further Reading</h4>
This plugin is developed and maintained by Colorlib. Which is well know for their free <a href="https://colorlib.com/wp/themes/" rel="nofollow ugc"></a>WordPress themes. However, now they are looking to extend their presence in plugin development and believe that FancyBox lightbox is a great way to start.
If you are new to WordPress and want to lear more we have got you covered. Colorlib will teach you have to <a href="https://colorlib.com/" rel="nofollow ugc">start a blog</a> or <a href="https://colorlib.com/wp/how-to-make-a-website/" rel="nofollow ugc">create a website</a> and much more. If you are already familiar with WordPress you likely want to learn how to make it faster and more reliable. That’s when you want to look into hosting and more specifically <a href="http://colorlib.com/wp/wordpress-hosting" rel="nofollow ugc">WordPress hosting</a>.
If you enjoy using FancyBox lightbox for WordPress please leave a <a href="https://wordpress.org/support/plugin/fancybox-for-wordpress/reviews/?filter=5" rel="ugc">positive feedback</a>. We are committed to make it the best lightbox plugin for WordPress.

FancyBox for WordPress

Seamlessly integrates FancyBox lightbox into your WordPress blog: Upload, activate, and you're done. Additional configuration optional.

Fancyboxify vs FancyBox for WordPress