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.

Tran Ngoc Tuan Anh

Meta Box

barcavn2

<a href="https://metabox.io/plugins/mb-rest-api/" rel="nofollow ugc">MB Rest API</a> is an extension for <a href="https://metabox.io" rel="nofollow ugc">Meta Box</a> which helps you to get and update custom fields’ values (meta value) from posts, pages, custom post types, terms via the WordPress REST API.
<blockquote>
Meta Box Lite 
 We recommend using <a href="https://metabox.io/lite/" rel="nofollow ugc">Meta Box Lite</a>, a feature-rich free UI version of Meta Box that provides UI and all free features for managing custom fields and dynamic content on WordPress, including post types, taxonomies, custom fields, and relationships.
</blockquote>
<h3>Plugin Links</h3>
<ul>
<li><a href="https://metabox.io/plugins/mb-rest-api/" rel="nofollow ugc">Project Page</a></li>
<li><a href="https://docs.metabox.io/extensions/mb-rest-api/" rel="nofollow ugc">Documentation</a></li>
<li><a href="https://github.com/rilwis/mb-rest-api/" rel="nofollow ugc">Github Repo</a></li>
</ul>
See more <a href="https://metabox.io/plugins/" rel="nofollow ugc">Meta Box plugins</a>.
<h3>You might also like</h3>
If you like this plugin, you might also like our other WordPress products:
<ul>
<li><a href="https://wpslimseo.com" rel="nofollow ugc">Slim SEO</a> – A fast, lightweight and full-featured SEO plugin for WordPress with minimal configuration.</li>
<li><a href="https://wpfalcon.pro" rel="nofollow ugc">Falcon</a> – A lightweight companion for making WordPress faster, cleaner, and more secure.</li>
<li><a href="https://gretathemes.com" rel="nofollow ugc">GretaThemes</a> – Free and premium WordPress themes that clean, simple and just work.</li>
<li><a href="https://wpautolistings.com" rel="nofollow ugc">Auto Listings</a> – A car sale and dealership plugin for WordPress.</li>
</ul>

MB Rest API

Get and update Meta Box custom fields to the WordPress REST API responses.

WP API Customizer vs MB Rest API