jakubkanna

This plugin forces all non-admin, non-AJAX, and non-REST API requests to return a 404 status code. 
Ideal for headless WordPress environments or sites that should expose only the API.

REST API Only

Force all non-admin, non-AJAX, and non-REST API requests to return a 404 for headless or API-only sites.

Benjamin Intal

gambitph

Using WordPress entirely as a CMS (a <a href="https://medium.com/@jchiatt/headless-wordpress-with-react-d573bca02ee0" rel="nofollow ugc">Headless WordPress</a>) is a plausible option for people building web apps using technologies such as React JS or Angular JS to entirely build their front-end.
Doing this, the front-end (e.g. built with React) becomes decoupled from the back-end (e.g. WordPress). Since WordPress is being used strictly to manage and serve the content via REST API, the WP front-end becomes unusable and unnecessary – hence the term “headless WordPress”.
This plugin essentially removes the front-end of WordPress.
<blockquote>
Note that the REST API, and other non-front-end stuff should work as normal.
</blockquote>
<h4>Features</h4>
<ul>
<li>No settings page</li>
<li>Allows backend access</li>
<li>Allows REST API endpoints</li>
<li>Redirects (403 Forbidden) all front-end pages to the login page</li>
</ul>

Redirect Front-end to Login | Headless WP

Redirects all front-end pages to the login page, best for building a headless WP REST API backend

REST API Only vs Redirect Front-end to Login | Headless WP