Scott Werner

When inserting an image into a post, WordPress uses absolute URLs to the files. This plugin overrides that functionality and forces it to use relative URLs.
For example:
WordPress Default: 
http://www.example.com/wp-content/uploads/2013/04/example.jpg
Plugin Override: 
/wp-content/uploads/2013/04/example.jpg
This is particularly useful if you plan on switching domains ever as well as reducing HTTP requests.

Relative Image URLs

Creates relative URLs for images when inserting into posts.

Andrzej Misiewicz

Simple Relative Urls plugin changes:
<ul>
<li>home and siteurl</li>
<li>script src urls</li>
<li>style link urls</li>
<li>images src urls</li>
</ul>
It uses wordpress filters. 
It doesn’t interact with database. 
It is fast, it doesn’t search and replace generated html. 
It doesn’t change hardcoded urls (for example in post content). 
It is flexible.
Plugin was originally created to enable wordpress to work with a <a href="https://www.npmjs.com/package/localtunnel" rel="nofollow ugc">localtunnel</a> npm package
<blockquote>
localtunnel exposes your localhost to the world for easy testing and sharing! No need to mess with DNS or deploy just to have others test out your changes.
</blockquote>
<h3>Example use cases</h3>
If Your development tasks don’t involve images, don’t download them from a server. Just install the plugin and add this line of code to your wp-config.php file
<pre><code>define( 'SRU_IMG_SRC_RELATIVE', false );
</code></pre>
Your local copy will then display images from their oryginal source.

Simple Relative Urls

This plugin makes urls (home url, js, css, images) across website relative. Works great with localtunnel npm package.

Relative Image URLs vs Simple Relative Urls