Lucy Tomas

Very simple plugin that will search for all the first images of your published posts, pages or custom post types and set them as the featured image.
<ul>
<li>You can choose the post type you want to run the plugin on.</li>
<li>Option to overwrite the already selected futured images.</li>
<li>Option to select From / To date.</li>
</ul>

Set All First Images As Featured

still works

It simply didn't recognize any images in any of the posts, and so didn't work. :(

Didn't see the images in the posts

IT works on 5.0.3

Sets the first image of your posts, pages or custom post types as the featured image.

danielpataki

Easy Featured Images allows you to assign featured images to posts much more efficiently, especially if you have a number of posts to go through. Normally you have to visit the edit page of each post, launch the media window and upload/assign the image.
With the plugin enabled you can do this from the post list screen. Everything words via AJAX so images are assigned instantly, without having to wait for pages to load. It uses the regular WordPress media box making the plugin 100% WordPress awesome.
Easy Featured Images also support WooCommerce, yay!
You can use the <code>efi/post_types</code> filter to modify the array of post types that the plugin’s functionality is assigned to. Return the final list of post types you want the plugin to be applied to:
<pre><code>add_filter( 'efi/post_types', 'my_post_type_images' );
function my_post_type_images( $post_types ) {
 unset( $post_types['page'] );
}
</code></pre>
As of 1.2.0 the plugin has an <code>efi/settings</code> filter which allows developers to change some settings. For now the only setting available is <code>show_thumbnail_preview</code> which can be set to true or false.
<pre><code>add_filter( 'efi/settings', 'my_efi_settings' );
function my_efi_settings( $settings ) {
 $settings['show_thumbnail_preview'] = false;
 return $settings
}
</code></pre>
<h4>Thanks</h4>
<ul>
<li><a href="https://tommcfarlin.com/the-wordpress-media-uploader/" rel="nofollow ugc">Tom McFarlin</a> for the basis of the Javascript that initiates the media uploader</li>
<li><a href="https://unsplash.com/colepatrick" rel="nofollow ugc">Cole Patrick</a> for the fantastic photo for the plugin’s featured image</li>
<li><a href="https://github.com/tmconnect" rel="nofollow ugc">Thomas Meyer</a> for the German translation.</li>
</ul>

Easy Featured Images

Allows you to add and remove featured images from admin post lists. Works with AJAX and magic for your image assignment pleasure.

Set All First Images As Featured vs Easy Featured Images