Bjørn Johansen

This is a WordPressified version of the excellent, lightweight (for real!) imageLightbox.js (MIT-licensed) by Osvaldas Valutis (http://osvaldas.info/image-lightbox-responsive-touch-friendly)
This is his introduction to the lightbox: 
“As for the image lightboxes, I have always lacked simplicity for them. I mean not only the visual design, but the overall experience: from implementation to UX. All due respect, but I have never liked any of these light-fancy-face-boxes. They all were solving problems that just don’t exist: lots of unwanted features by default, total mess in markup, no native behavior for touch screens. I was working on a project and needed an image lightbox that solves these problems. I needed a lightbox only for images, not video, text, and iframes at once. I made ImageLightbox.js.”
This version autodetects all links to image files and opens them in the lightbox.
For your “install, activate and go”-convenience, this plugin comes with a minimal CSS that easily can be deactivated and/or replaced.
The plugin can also be themed to your liking. An example theme is available here: https://github.com/bjornjohansen/imagelightbox-theme-smooth
Please let me know if you have any issues. Fastest way to get a response is by Twitter: https://twitter.com/bjornjohansen

imageLightbox

Image Lightbox, Responsive and Touch‑friendly.

wpszaki

If you are embedding Youtube video(s) into your site then you will need this plugin. As you may (or may not) know the default Youtube embed code is not responsive and in order to load the player itself your browser has to download more than 1MB of data from Youtube’s servers. That is way too much and this is the reason why we made this plugin. A video player has to be lightweight and responsive. Period.
This plugin is replacing the default Youtube player with the video’s high quality thumbnail and a play button. The real player and the video won’t load until you click on the play button or the thumbnail itself. With this easy trick you will have a much lighter and faster website and the thumbnail + the actual player will be responsive too.
Our plugin is only 60KB without any extra library or unnecessary function.
If you are speed-optimizing your site or if you want to reduce the loading times of your pages then you are at the right place.
<h3>This plugin will:</h3>
<ul>
<li>Make all of the embedded Youtube videos responsive automatically</li>
<li>Will reduce the size of your pages (where you have embedded videos)</li>
<li>Will make your site faster</li>
<li>Will improve the user experience</li>
</ul>
<h3>You can also:</h3>
<ul>
<li>
Manually insert a different thumbnail for each embedded video with the ‘thumb_url’ parameter.
[youtube_embed url=”video_url” thumb-url=”custom_thumb_url”]
</li>
<li>
Manually set a different width for each video with the ‘width’ parameter.
[youtube_embed url=”video_url” width=”50″]
</li>
<li>
Manually align each video to left, right or center with the ‘align’ parameter.
[youtube_embed url=”video_url” align=”center”]
</li>
<li>
Disable the related videos
</li>
<li>Disable the video controls</li>
<li>Disable the fullscreen option</li>
<li>Align the videos globally or individually</li>
<li>Set the custom video width for all videos or to just a single video with a shortcode parameter</li>
</ul>
<h3>Comparison</h3>
Here’s a quick comparison with the built-in TwentySeventeen theme (without any other plugin).
We placed a default Youtube video embed code in a new and empty page, ran the tests and then replaced it with our solution before running the tests again.
Total page size with the traditional Youtube embed code: 2.18MB 
Total page size with our lightweight & responsive embedder: 472KB
Page load time with the traditional Youtube embed code: 5.33s 
Page load time with our lightweight & responsive embedder: 2.52s

Lightweight and Responsive Youtube Embed

Make your embedded Youtube videos responsive & lightweight with this plugin. Reduce the loading time of your site and increase the user experience …

imageLightbox vs Lightweight and Responsive Youtube Embed