Kite

Due to security/privacy concerns, JSON REST API (WP API) only allows post meta data (custom field value) for authenticated users. 
This plugin is an easy way to make post meta available when unauthenticated.
After activate the plugin, go to WP API Customizer option page. 
Click the plus icon to add rows. 
Set JSON attributes and custom field names in your posts that you want to use when unauthenticated. 
The JSON REST API will provide the data as “post_meta” like the following:
<pre><code>"post_meta":{"your_attribute_a":"Custom Field A value","your_attribute_b":"Custom Field B value"}
</code></pre>

WP API Customizer

Make post meta data (custom field values) available for JSON REST API (WP API) when unauthenticated.

Brian Zoetewey

Apollo139

jayque9

barclay_reg

This is an add-on for the <a href="https://wordpress.org/extend/plugins/advanced-custom-fields/" rel="ugc">Advanced Custom Fields</a> WordPress plugin and will not provide any functionality to WordPress unless advanced Custom Fields is installed and activated.
The NextGEN Gallery field provides a dropdown (select or multi-select) of NextGEN Gallery names (galleries and albums) and the ability to map the selected NextGEN Gallery to the post. 
The get_value() API returns an array of the selected NextGEN Gallery IDs and the form – album or gallery.
Support ACF5 Pro, ACF4, ACF3, NextCellent Gallery – NextGEN Legacy.
!!! Version 1.1 !!! 
This version changes get_value() API returned value. You must change your template files. !!!
The get_value() API returns a following array: 
 Array ( 
 [0] => Array ( 
 [ngg_id] => 8 ( NextGEN Gallery ‘gallery’ or ‘album’ ID ) 
 [ngg_form] => gallery ( ‘gallery’ or ‘album’ ) 
 ) 
 )
<h4>Example</h4>
These examples should show a NextGEN Gallery gallery or NextGEN Gallery album.
For version 1.1 and later
 
For version 1.0.2 and earlier

Advanced Custom Fields: NextGEN Gallery Field add-on

Adds a NextGEN Gallery Field to Advanced Custom Fields. Select one or more NextGEN Galleries and assign them to the post.

WP API Customizer vs Advanced Custom Fields: NextGEN Gallery Field add-on