<h4>Why this plugin exists</h4>
Original Plugin (discontinued): https://de.wordpress.org/plugins/json-ld-for-article/
Sadly, the original plugin is not being developed anymore. So I decided to fix some bugs like invalid markup, 
 missing tags, putting objects into fields instead of just URLs for images, and implementing for more than just 
 articles.
Also, this plugin plays nicely with <a href="https://de.wordpress.org/plugins/yet-another-stars-rating/" rel="nofollow ugc">YASR – yet another star rating</a>. It will 
remove yasr’s invalid jsonld-syntax and instead use YASRs rating.
All requests are being cached and purged on page update/edit etc.
<a href="https://waffle.io/bmhm/wp-jsonld" rel="nofollow ugc"></a>
<h4>Original description</h4>
Search engines such as Google are using structured data markup in many ways—for example, to create rich snippets in search results. Search results with rich snippets will improve your click through rates and increase the number of visitors on your website.
It has been a tedious task to add the complicated Schema.org markup to your website – sometimes it wasn’t even possible due to technical constraints. Now, thanks to JSON-LD, almost any website can enjoy the benefits of structured data. For WordPress users it’s even easier thanks to this plugin.
JSON-LD for Article is simply the easiest solution to create valid schema.org microdata markup on your WordPress site automatically from your web content and its metadata. All you need to do is install and activate the plugin, and it will generate JSON-LD markup of your posts that Google and other search engines can use for rich snippets using the schema.org for articles.
Some WP themes include traditional schema.org markup embedded in the html code the theme produces. If you are using one of these themes, this plugin is probably not necessary. If the markup produced by the theme contradicts the data specified in the JSON-LD, the added information might be not be helpful at all. Thus you should check the markup provided by the theme before adding possibly unnecessary JSON-LD to your site.
On the other hand, if you use a custom theme, it is easier to use the functionality provided by the plugin than to invent the wheel again and add the markup in html. Very often, this leads to html code that is difficult to read and is not valid structural markup according to Google’s validator.
Our plugin:
<ul>
<li>Helps your site to earn rich snippets in Google’s SERP.</li>
<li>Does not depend on other plugins or external code.</li>
<li>Is simple to install: plug-and-play, no need to configure anything.</li>
</ul>

wp-jsonld

wp-jsonld is the continuation of the simplest solution to add valid schema.org microdata as JSON-LD-script to your blog posts and articles.

mborgelt

51Blocks JSON Schema Creator allows business owners to add schema markup to a single page or entire site without outputting the markup on the actual site. This tool also makes it very easy to validate your markup against Google Structure data testing tool
Schema is the result of collaboration between Google, Bing, Yandex, and Yahoo! to help you provide the information their search engines need to understand your content and provide the best search results possible at this time.

51Blocks JSON Schema Generator

51Blocks JSON Schema Creator allows business owners to add schema markup to a single page or entire site.

wp-jsonld vs 51Blocks JSON Schema Generator