Definite is the first theme we have incorporated a lightbox when you create galleries with the WordPress Gallery Shortcode. Originally we sent you to an image (attachment) page with a viewer, but it just wasn’t as pleasant as we had hoped for. We decided to implement a lightbox (the ColorBox lightbox script) into this theme which now displays your gallery images in a popup overlay viewer.
This is disabled by default, but you can enable it if you decide to use the WordPress Gallery shortcode. One added bonus is that we made this compatible with the Gutenberg block editor’s own gallery block.
Go to Appearance >> Customize >> Theme Options >> Basic Settings
Look for the “Enable the Gallery Lightbox” setting and check the box to enable the lightbox.
Click “Save & Publish“.
Make Your Gallery Open in the Lightbox
Once you make your gallery, you will want to link your thumbnails to the “Media” option in the gallery settings. This will enable the lightbox when someone clicks on a thumbnail.