Bage

Modal windows are interesting way to include extran information on a page. <a href="http://www.onextrapixel.com/2014/06/25/create-modal-windows-that-can-be-morphed-from-anything-with-jquery-adaptive-modal-js/" rel="nofollow ugc">adaptive-modal.js</a> makes it beautiful. You can use this little plugin which uses the same jQuery plugin to creae modal windows easily in any page or post or even on a widget uisng shortcode.
I have also added another functionality into this plugin, which will let you to embed your modal content into your post a page directly.
<h3>Usage</h3>
Upon activation, the plugin will create a custom post type called ‘Modals’. Where you can add your content, which later you can use it on a modal or embed directly into your page or post.
<ol>
<li>[modal]</li>
<li>[block] </li>
</ol>
<h3>modal</h3>
the ‘modal’ shortcode is to create modal windows.
For now the [modal] shortcode comes with four attributes.
id 
Your modal id. eg: [modal id=2]Click here[/modal]
data 
If your modal only going to have just text, you can directly add the content in the shortcode. eg: [modal data=”This is my modal content”]Click here[/modal]. This shortcode is much useful when you want to add a modal window to a word in a paragrap without braking the paragrap.
<pre><code>note: you cannot use both id and data in the same shortcode
</code></pre>
background 
This is to style the link and the modal window background. Have to specify a valid color. eg: [modal id=2 background=”#DDDDDD”]Click here[/modal]
color 
This attribute is to change the color of the link. eg: [modal id=2 background=”#DDDDDD” color=”#000000″]Click here[/modal]
<h3>block</h3>
The ‘block’ shortcode is to embed your modal content into any page or post. It only has one attribute.
id 
id of the modal post type post.
<pre><code>note: both block and modal shortcodes uses the same Modals custom post type.
</code></pre>

Flexible Modals

Flexible Modal is a very simple plugin to add modal windows to your WordPress content using shortcodes.

Aman

webholics

Popup Addon for Ninja Forms allows you to show any Ninja Forms in Popup/Modal. 
You can create beautiful popups with live preview in customizer. 
It allows you add additional content before & after the form in popup. 
Popup can be triggered by click or can be opened on page load using the shortocde.
<h3>Top Features:</h3>
<ul>
<li>Option to set Popup Cookie to hide it after opened certain number of times.</li>
<li>Option to set Popup Animations.</li>
<li>Option to set Popup Container Width for mobile.</li>
<li>Option to set Popup Container Height for mobile.</li>
<li>Option to set Overlay color.</li>
<li>Option to set Overlay opacity.</li>
<li>Option to set Popup Container opacity.</li>
<li>Option to set Popup Container background color.</li>
<li>Option to set Popup Container Padding.</li>
<li>Option to set Popup Container Border.</li>
<li>Option to set Popup Container Rounded Corners.</li>
<li>Option to set Popup Container Width.</li>
<li>Option to set Popup Container Height.</li>
<li>Option to open popup by any link using class or ID.</li>
</ul>
Get more features in <a href="https://webholics.org/downloads/popup-add-on-for-ninja-forms-pro/?utm_source=wordpress-plugin-repo&utm_medium=popup-addon-for-ninja-forms&utm_campaign=popup-addon-for-ninja-form-lite-version" rel="nofollow ugc">Pro version</a> 
* Advanced Animations 
* Exit Intent 
* Hide Popup on Mobile/Desktop. 
<a href="https://webholics.org/downloads/popup-add-on-for-ninja-forms-pro/?utm_source=wordpress-plugin-repo&utm_medium=popup-addon-for-ninja-forms&utm_campaign=popup-addon-for-ninja-form-lite-version" rel="nofollow ugc">Get Popup Addon for Ninja Forms PRO!</a>

Popup addon for Ninja Forms

Please give it a try & send feedback if you have any.
Would love to hear it.

Great Plugin for adding popup/modal to ninja forms

Popup/Modal addon for Ninja Forms. Create beautiful popups using Ninja Forms for newsletters, login, registration forms.

Flexible Modals vs Popup addon for Ninja Forms