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.

Felix Arntz

This plugin takes a no-frills approach to smooth scrolling, providing a fast, performant, and accessible user experience.
Simply enable the plugin, and any anchor links (i.e. links that point to other content on the same page) will provide a smooth scrolling experience rather than abruptly jumping to the destination content.
The plugin relies on the latest smooth scrolling techniques using CSS. A very fast and lightweight JavaScript polyfill (<1KB) is included to equally support older browsers, including Internet Explorer. So you can rest assured this plugin covers your userbase.
<h4>Why does this plugin exist?</h4>

Smooth scrolling is a basic feature to enhance user experience, so it shouldn’t come at a performance cost that at the same time harms user experience elsewhere.
Several other smooth scrolling solutions unfortunately rely on outdated techniques such as jQuery, which can hurt your site’s performance, and is really not necessary to provide the feature. Even browsers as old as 10 years don’t need jQuery to achieve smooth scrolling. In fact, as of today you can achieve the behavior with only CSS, not even requiring any JavaScript.
Another potential reason to use this plugin over other smooth scrolling solutions is accessibility: This plugin respects the user preferences around reduced motion, which can avoid discomfort for those with <a href="https://www.a11yproject.com/posts/understanding-vestibular-disorders/" rel="nofollow ugc">vestibular motion disorders</a>.
You may already use a smooth scrolling plugin, but it is worth double checking that it doesn’t use one of those outdated, inefficient, and inaccessible approaches that may slow down your site or affect user interactions negatively.
<h4>More technical details</h4>
This plugin simply enables smooth scrolling with the <code>scroll-behavior</code> CSS property. This property has been supported by all modern browsers for a few years now.
To support older browsers as well, a lightweight JavaScript polyfill is included, which is only loaded for browsers that lack support for the CSS property and doesn’t require any dependencies. The polyfill uses latest JavaScript user experience best practices such as <code>requestAnimationFrame</code> to provide a smooth scrolling experience without potentially blocking other user interactions.
For relevant browser support, see: 
* <a href="https://caniuse.com/css-scroll-behavior" rel="nofollow ugc">CSS Scroll-behavior</a> 
* <a href="https://caniuse.com/mdn-css_properties_scroll-padding-top" rel="nofollow ugc">CSS property: scroll-padding-top</a> 
* <a href="https://caniuse.com/prefers-reduced-motion" rel="nofollow ugc">prefers-reduced-motion media query</a> 
* <a href="https://caniuse.com/requestanimationframe" rel="nofollow ugc">requestAnimationFrame</a> 
* <a href="https://caniuse.com/high-resolution-time" rel="nofollow ugc">High Resolution Time API</a> 
* <a href="https://caniuse.com/mdn-api_nodelist" rel="nofollow ugc">NodeList API</a> 
* <a href="https://caniuse.com/mdn-api_window_scrollto" rel="nofollow ugc">Window API: scrollTo</a>

Fast Smooth Scroll

This lightweight plugin enhances user experience by enabling smooth scrolling for anchor links without the need for jQuery or other dependencies.

imageLightbox vs Fast Smooth Scroll