OpenGG

Simple and small lightbox clone, Modded from Joel Vardy’s lightbox, more info at http://blog.ilooker.tk/
Download and install, that’s all you need to do. And when you post articles with images, this plugin (the js script actually) will automatically lightbox those unlinked images (would not affect those images with links).
For example, I posted an article, with two image unlinked to anything (let’s call them image1 and image2), one image linked to another webpage (called image3). Then when someone click on these three images, image1 and image2 will be lightboxed but image3 will not.
Demos: 
<a href="https://jquery-littlebox-for-wp.googlecode.com/svn/trunk/demo.htm" title="Demo on Googlecode" rel="nofollow ugc">Demo on Googlecode</a> 
<a href="http://blog.ilooker.tk/" title="My blog" rel="nofollow ugc">My blog</a>
<h3>Issue list</h3>
<ul>
<li>Large image overflowing issue;</li>
<li>Iframes and flash objects unsupported yet;</li>
<li>Image groups unsupported yet (one click one image, no prev/next);</li>
<li>Not so customizable for users yet;</li>
<li>UI design improving needed.</li>
</ul>

jQuery Littlebox for WP

Simple and small lightbox clone, Modded from Joel Vardy's lightbox, more info at http://blog.ilooker.tk/

WordPress.org

This plugin captures real user metrics about what elements are displayed on the page across a variety of device form factors (e.g. desktop, tablet, and phone) in order to apply loading optimizations which are not possible with WordPress’s current server-side heuristics.
This plugin is a framework dependency which does not provide optimization functionality on its own. For that, please install the <a href="https://wordpress.org/plugins/image-prioritizer/" rel="ugc">Image Prioritizer</a> and <a href="https://wordpress.org/plugins/embed-optimizer/" rel="ugc">Embed Optimizer</a> dependent plugins (among <a href="https://github.com/WordPress/performance/labels/%5BPlugin%5D%20Optimization%20Detective" rel="nofollow ugc">others</a> to come from the WordPress Core Performance team). There are currently no settings and no user interface for this plugin since it is designed to work without any configuration.
Your site must currently have the REST API accessible to unauthenticated frontend visitors since this is how real user metrics are collected about pages on your site; nevertheless, <a href="https://github.com/WordPress/performance/issues/1311" rel="nofollow ugc">exploration</a> is underway for providing alternative mechanisms for collecting the metrics. Also, please note that no metrics are currently collected from Safari since it does not yet support the <a href="https://developer.mozilla.org/en-US/docs/Web/API/LargestContentfulPaint" rel="nofollow ugc">Largest Contentful Paint</a> metric, but support for this <a href="https://web.dev/explore/learn-core-web-vitals" rel="nofollow ugc">Core Web Vitals</a> metric is coming this year <a href="https://webkit.org/blog/16458/announcing-interop-2025/#core-web-vitals" rel="nofollow ugc">via Interop 2025</a>.
Please refer to the <a href="https://github.com/WordPress/performance/blob/trunk/plugins/optimization-detective/docs/README.md" rel="nofollow ugc">full plugin documentation</a> for a <a href="https://github.com/WordPress/performance/blob/trunk/plugins/optimization-detective/docs/introduction.md" rel="nofollow ugc">technical introduction</a>, <a href="https://github.com/WordPress/performance/blob/trunk/plugins/optimization-detective/docs/hooks.md" rel="nofollow ugc">filter/action hooks</a>, and <a href="https://github.com/WordPress/performance/blob/trunk/plugins/optimization-detective/docs/extensions.md" rel="nofollow ugc">extensions</a> that show use cases and examples. You can also watch the talk from WordCamp Asia 2025: <a href="https://weston.ruter.net/2025/02/21/boosting-performance-with-optimization-detective/" rel="nofollow ugc">Boosting Performance with Optimization Detective</a>.

Optimization Detective

Provides a framework for leveraging real user metrics to detect optimizations for improving page performance.

jQuery Littlebox for WP vs Optimization Detective