wpcocktail

The Site Title Caption Modifier is a simple WordPress plugin that sets the caption of all images in your WordPress site to the site title. This is particularly useful for maintaining a consistent branding or style across all posts and pages. The plugin works by hooking into the WordPress ‘img_caption_shortcode’ filter and modifying the caption output.

Image Caption for WP

Automatically sets the caption of all images to your site's title.

nicmare

WordPress ships with a native Lightbox-Effect for image blocks. This plugin adds one tiny additional option to the core image and gallery blocks: <code>Show Caption</code>.
When the toggle is enabled, the native lightbox receives the current image alt text as a <code>data-img-alt</code> attribute on the enlarged lightbox figure. A small frontend CSS then displays that value as a caption overlay inside the lightbox image.
Please note: The caption text is taken from the image <code>alt</code> attribute.
The toggle is only available when the native Lightbox-Effect is active. If the lightbox is disabled or the image is linked somewhere else, the caption option is disabled as well.
<h3>Plugin Features</h3>
✔ adds a new toggle <code>Show caption</code> to the core Image block 
✔ adds the same toggle to the core Gallery block 
✔ the toggle can only be enabled when the native Lightbox-Effect is active 
✔ ships with German translation files for the editor toggle 
✔ uses the image <code>alt</code> attribute as value for <code>data-img-alt</code> 
✔ adds the attribute only to the enlarged image figure in the lightbox 
✔ supports galleries by passing the gallery setting to the nested image blocks 
✔ outputs the value with a lightweight frontend CSS pseudo element 
✔ uses no new block and does not replace the existing Image or Gallery blocks

LMDM Lightbox Image Caption

Adds a lightbox-only image caption toggle for core Image and Gallery blocks.

Image Caption for WP vs LMDM Lightbox Image Caption