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

Van Quyen

MB FacetWP Integration is a free plugin that integrates <a href="https://metabox.io" rel="nofollow ugc">Meta Box</a> and <a href="https://facetwp.com" rel="nofollow ugc">FacetWP</a>, which makes custom fields of Meta Box searchable and filterable in the frontend.
<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>
For an e-commerce or a listing website, the product or listing requires custom data such as price, location, color, etc. And users need to search or filter the products / listings in the frontend based on these criteria.
<ul>
<li>With the help of Meta Box, you can create any kind of data (custom fields) for your product / listing or any custom post type.</li>
<li>And FacetWP will make products / listings searchable, filterable by those data.</li>
</ul>
This plugin doesn’t require any configuration. Just install it and you will see Meta Box custom fields appear in the list of options in FacetWP settings.
<h3>Plugin Links</h3>
<ul>
<li><a href="https://metabox.io/plugins/meta-box-facetwp-integrator/" rel="nofollow ugc">Homepage</a></li>
<li><a href="https://github.com/wpmetabox/meta-box-facetwp-integrator/" rel="nofollow ugc">Github repo</a></li>
<li><a href="https://metabox.io/plugins/" rel="nofollow ugc">View other premium extensions</a></li>
</ul>
<h3>Other products</h3>
If you love this plugin, please try our other great products:
<ul>
<li><a href="https://wpslimseo.com" rel="nofollow ugc">Slim SEO</a>: A lightweight and full-featured SEO plugin for WordPress</li>
<li><a href="https://wpslimseo.com/products/slim-seo-schema/" rel="nofollow ugc">Slim SEO Schema</a>: The best schema plugin for WordPress</li>
<li><a href="https://wpslimseo.com/products/slim-seo-link-manager/" rel="nofollow ugc">Slim SEO Link Manager</a>: Build internal links easier in WordPress</li>
<li><a href="https://wpautolistings.com" rel="nofollow ugc">Auto Listings</a>: The car sale and dealership plugin for WordPress</li>
<li><a href="https://gretathemes.com" rel="nofollow ugc">GretaThemes</a>: Beautiful and easy to use WordPress themes</li>
</ul>

MB FacetWP Integration

Integrates Meta Box custom fields with FacetWP. Make custom fields filterable.

WP API Customizer vs MB FacetWP Integration