MarcusPope

A WordPress plugin that converts all URL formats to root-relative URLs to enable seamless transitioning between staging/production host environments and debugging/testing from mobile devices, without the use of hackish tactics like textual find-replace strategies or risky hosts/NAT spoofing strategies.
With Root Relative URLs you can browse your development site from http://localhost/ or http://127.0.0.1/ or from a named network resource like http://mycomputername/ without worrying about links redirecting you back to your site’s URL.
This plugin also modifies the tinyMCE hooks so links and media embedded with built-in tools will only insert URLs from the first forward slash after the domain (i.e. the root of your site.) This means when you push content changes to a staging or production environment they are guaranteed to reference the correct target instead of accidentally referencing a production resource in development or, worse-yet, a development-exclusive resource in production.
It supports path-based MU Installations, but does not support domain-based MU sites due to architectural deficiencies in the WordPress core.
Version 1.5 fixes an infinite redirect problem that is a result of a core bug in WordPress. If you have problems with the <!–more–> tag or permalinks for custom post types, please read the FAQ or new Install Steps for support.
Version 2.2 allows for adding certain URL’s or partial URL’s to a blacklist, meaning I won’t use root relative urls, but dynamic absolute URLs instead for displaying content. This will fix problems with 3rd party plugins, and can be configured on the General Settings page.
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Root Relative URLs

Converts all URLs to root-relative URLs for hosting the same site on multiple IPs, easier production migration and better mobile device testing.

Marco Milesi

WP Post Redirect allows you to seamlessly redirect individual posts to external URLs or internal content. Once activated, a new metabox appears on the post edit screen, letting you specify a custom redirect URL or search for an internal post/page. Great for affiliate links, content curation, or moving content.
Features: 
* Add a redirect URL to any post via a simple metabox. 
* Search and select internal posts or pages for redirection. 
* Set custom HTTP Status codes (301, 307, 308) globally or per post. 
* Option to open redirects in a new tab and allow <code>rel="nofollow"</code>. 
* Highlight posts with active redirections in the admin area. 
* Dashboard options page to manage all redirections with CSV Export. 
* Backend column to mark posts with redirect enabled. 
* Lightweight and easy to use. 
* Fully compatible with the latest WordPress versions.

WP Post Redirect

Easily redirect your WordPress posts to any external URL with a simple metabox. Lightweight, efficient, and perfect for SEO!

Root Relative URLs vs WP Post Redirect