Directory / plugin
Relative Image URLs
v2.0 · by Scott Werner
Creates relative URLs for images when inserting into posts.
About this plugin
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.