Milan Dinić

<a href="http://blog.milandinic.com/wordpress/plugins/descriptions-as-captions-in-galleries/" rel="nofollow ugc">Plugin homepage</a> | <a href="http://blog.milandinic.com/" rel="nofollow ugc">Plugin author</a> | <a href="http://blog.milandinic.com/donate/" rel="nofollow ugc">Donate</a>
Image descriptions are stored as content (field <code>post_content</code>) while captions are stored as excerpt (field <code>post_excerpt</code>). This means that descriptions are shown on single attachment pages, while captions are shown in <a href="https://codex.wordpress.org/Gallery_Shortcode" rel="nofollow ugc">galleries</a> and if image is embedded in a post content with a <code>[caption]</code> shortcode.
If you use images just in galleries, in order to have text below image in both places, you need to fill both fields.
This plugin changes that. You only fill description field and that text is used as caption of image in galleries.
There are no options or settings, just enable plugin and everything works automatically.

Descriptions as Captions in Galleries

Show image descriptions as captions in galleries.

Terry Chay

The core <a href="https://developer.wordpress.org/reference/functions/img_caption_shortcode/#source-code" rel="nofollow ugc"><code>img_caption_shortcode()</code></a> function <a href="https://core.trac.wordpress.org/ticket/24990#comment:13" rel="nofollow ugc">doesn’t process shortcodes when they’re in the caption (just when they’re in the image)</a>. This simple plugin changes it so that captions can contain shortcodes.
It also fixes some other small edge-case bugs in the original code.

Nested image caption shortcode

Allows caption shortcode to have shortcodes

Descriptions as Captions in Galleries vs Nested image caption shortcode