yorksupport

York IE – Theme Switcher lets editors assign a theme to a single piece of content or preview how that content looks in another installed theme. The site-wide active theme stays unchanged.
Features
<ul>
<li>Assign a theme per post, page, or public custom post type</li>
<li>Settings page to enable theme switching per post type</li>
<li>Preview any supported item with another installed theme in a new tab</li>
<li>Content Theme meta box in the editor sidebar</li>
<li>Front-end admin bar menu for quick theme previews while logged in</li>
<li>Preview banner with an exit link when previewing</li>
<li>Works with subdirectory WordPress installs</li>
</ul>
How it works
<ol>
<li>Edit a post, page, or custom post type.</li>
<li>Choose a theme from the Content Theme sidebar panel.</li>
<li>Click Update to save the assignment, or use Preview with selected theme to test without saving.</li>
</ol>
Visitors see the assigned theme only on that content item. Other pages continue using the active site theme.
Permissions
<ul>
<li>Theme preview URLs require a valid nonce and permission to edit the item or the <code>switch_themes</code> capability.</li>
<li>Assigned themes are visible to all visitors on the front end for that content item.</li>
</ul>
Developer filters
<ul>
<li><code>pagethsw_supported_post_types</code> — Limit or extend supported post types.</li>
<li><code>pagethsw_is_supported_post_early</code> — Control post type support before <code>init</code>.</li>
</ul>

York IE – Theme Switcher

Assign or preview a different installed theme on individual posts, pages, and custom post types without changing the site-wide active theme.

martenmoolenaar

Zodan

When we are developing themes, we quite often like to switch between the old (active) and the new (to develop) version of a theme. Sometimes without other people noticing. 
This plugin does exactly that.
<h4>What does it do?</h4>
It lets users with certain roles see another (than the currently active) theme, by 
* Selecting a theme from the list of installed themes 
* Selecting which user roles are permitted to switch themes and 
* Optionally, selecting user roles that can use a ‘switch theme/back’ button on the front-end
This plugin is under active development. Any feature requests are welcome at <a href="plugins@zodan.nl" rel="nofollow ugc">plugins@zodan.nl</a>!

Zodan Theme Switcher


Z Theme Switcher has quickly become one of my favourite tools when working on new WordPress themes. It solves a very specific problem in a clean and effective way: being able to preview a different theme — just for yourself or selected user roles — without changing the live site for visitors.



What I really like:




It’s lightweight and easy to set up



You can control exactly who sees the development theme



The optional front-end switch button is handy during testing



It keeps everything safe and invisible to regular users




I often need to develop or fine-tune a new design while a site stays online. With this plugin, I can work directly on the live server, test things in context, or share previews with clients — all without setting up a separate staging environment.



It’s clear the developer understands real-world needs. The plugin is actively maintained and feels reliable. If you work with custom themes, this is definitely worth adding to your toolkit.


A simple but very useful tool for theme developers

Allow (certain) users(roles) to easily switch to another theme. Non-persistent, so regular users won't be bothered.

York IE – Theme Switcher vs Zodan Theme Switcher