Jeff Starr

Theme switching done right.
<blockquote>
Preview any theme privately on the front-end 
 Develop themes privately behind the scenes 
 Enable your visitors to switch themes
</blockquote>
There are many theme-switcher plugins but none of them provide the simplicity, performance, and reliability that I require for my own sites. So I wrote my own plugin using the WP API and kept the plugin as focused and solid as possible. Only essential theme-switching features have been added, along with a simple yet informative UI. This gives you a consistent, quality theme-switching experience that you can optionally share with your visitors.
<blockquote>
Switch to an alternate theme for preview or development while visitors use the default theme 🙂
</blockquote>
What it’s for..
Theme Switcha:
<ul>
<li>Enables visitors to switch themes via the frontend</li>
<li>Enables admins to test alternate themes for debugging</li>
<li>Enables developers to build/customize themes privately</li>
<li>Enables you to create links that switch to specific themes</li>
<li>Enables live private previews of any installed theme</li>
</ul>
What it’s NOT for..
This plugin should not be used together with WordPress features such as the Theme Customizer, Widgets, and Menus. Doing so may result in private changes being made public on the current active theme. <a href="https://wordpress.org/support/topic/important-please-read-3/" rel="ugc">Learn more</a>.
<blockquote>
Theme Switcha = Best Theme Switcher for WordPress
</blockquote>
Plugin Features
<ul>
<li>Develop new themes while visitors use the default theme</li>
<li>Control who can switch themes (admins, w/ passkey, or everyone)</li>
<li>Administrators can switch themes directly via the WP Admin Area</li>
<li>Enable visitors to switch and preview themes on the front-end</li>
<li>Each visitor can choose their own theme</li>
<li>Send preview links to clients via the passkey</li>
<li>Choose your own custom passkey code for preview links</li>
<li>Set the duration (cookie timeout) for switched themes</li>
<li>Enable/disable theme preview in the Admin Area</li>
<li>Enable/disable all theme switching without deactivating the plugin</li>
<li>Provides several shortcodes to enable visitors to switch themes</li>
<li>Shortcodes display themes as a list, select menu, or thumbnails</li>
<li>Changed options are saved when working on switched themes</li>
<li>Dashboard widget to switch themes via select menu</li>
<li>Simple, stylish UI featuring screenshots of each theme</li>
<li>Works with any theme, parent themes and child themes</li>
<li>Works with or without Gutenberg Block Editor</li>
<li>Works with WP Multisite</li>
</ul>
Theme Switcha makes it easy for the site admin to preview and develop new themes without changing the default theme. So visitors will continue to use your site normally without ever knowing that you are testing new themes behind the scenes. And if you want to enable your visitors to switch themes, you can do that as well by adding a shortcode to any WP Post or Page. Then each visitor will be able to select and preview any of your WordPress themes.
Core Features
<ul>
<li>Easy to use</li>
<li>Squeaky clean code</li>
<li>Simple and focused</li>
<li>Built with the WordPress API</li>
<li>Lightweight, fast and flexible</li>
<li>Focused on performance and security</li>
<li>Regularly updated and “future proof”</li>
<li>Works great with other WordPress plugins</li>
<li>Plugin options configurable via settings screen</li>
<li>Plugin cleans up after itself upon uninstall</li>
<li>One-click restore plugin default options</li>
</ul>
Plus you get free, responsive support from a top WP professional 😉
The Theme Switcha plugin is useful for things like:
<ul>
<li>Maintenance mode – display a temporary theme to visitors while you update your primary theme</li>
<li>Theme test drive – preview and test new themes without disrupting anything on the frontend</li>
<li>Debugging Themes – test and troubleshoot issues that may be related to the current active theme</li>
<li>Theme development – perfect for developing new theme templates to fit existing site content</li>
<li>Client presentations – send clients special “theme preview” links to show off new templates</li>
</ul>
I use Theme Switcha to develop new themes for my own sites like <a href="https://perishablepress.com/" rel="nofollow ugc">Perishable Press</a> and <a href="https://plugin-planet.com/" rel="nofollow ugc">Plugin Planet</a>. The beauty of Theme Switcha is that visitors will never know that you are hard at work testing and building new themes behind the scenes 🙂
Privacy
This plugin does not collect or store any user data. It does not set any user cookies, and it does not connect to any third-party locations. Thus, this plugin does not affect user privacy in any way.
Theme Switcha is developed and maintained by <a href="https://x.com/perishable" rel="nofollow ugc">Jeff Starr</a>, 15-year <a href="https://plugin-planet.com/" rel="nofollow ugc">WordPress developer</a> and <a href="https://books.perishablepress.com/" rel="nofollow ugc">book author</a>.
Support development
I develop and maintain this free plugin with love for the WordPress community. To show support, you can <a href="https://monzillamedia.com/donate.html" rel="nofollow ugc">make a donation</a> or purchase one of my books:
<ul>
<li><a href="https://wp-tao.com/" rel="nofollow ugc">The Tao of WordPress</a></li>
<li><a href="https://digwp.com/" rel="nofollow ugc">Digging into WordPress</a></li>
<li><a href="https://htaccessbook.com/" rel="nofollow ugc">.htaccess made easy</a></li>
<li><a href="https://wp-tao.com/wordpress-themes-book/" rel="nofollow ugc">WordPress Themes In Depth</a></li>
<li><a href="https://books.perishablepress.com/downloads/wizards-collection-sql-recipes-wordpress/" rel="nofollow ugc">Wizard’s SQL Recipes for WordPress</a></li>
</ul>
And/or purchase one of my premium WordPress plugins:
<ul>
<li><a href="https://plugin-planet.com/bbq-pro/" rel="nofollow ugc">BBQ Pro</a> – Blazing fast WordPress firewall</li>
<li><a href="https://plugin-planet.com/blackhole-pro/" rel="nofollow ugc">Blackhole Pro</a> – Automatically block bad bots</li>
<li><a href="https://plugin-planet.com/banhammer-pro/" rel="nofollow ugc">Banhammer Pro</a> – Monitor traffic and ban the bad guys</li>
<li><a href="https://plugin-planet.com/ga-google-analytics-pro/" rel="nofollow ugc">GA Google Analytics Pro</a> – Connect WordPress to Google Analytics</li>
<li><a href="https://plugin-planet.com/head-meta-pro/" rel="nofollow ugc">Head Meta Pro</a> – Ultimate Meta Tags for WordPress</li>
<li><a href="https://plugin-planet.com/simple-ajax-chat-pro/" rel="nofollow ugc">Simple Ajax Chat Pro</a> – Unlimited chat rooms</li>
<li><a href="https://plugin-planet.com/usp-pro/" rel="nofollow ugc">USP Pro</a> – Unlimited front-end forms</li>
</ul>
Links, tweets and likes also appreciated. Thank you! 🙂
<h3>Credit</h3>
Thanks to Ryan Boren for the original <a href="https://plugins.trac.wordpress.org/wiki/ThemeSwitcher" rel="nofollow ugc">Theme Switcher</a> plugin.

Theme Switcha – Easily Switch Themes for Development and Testing

I dealt with Jeff about 2 years ago, and though his website blog and code snippets, all I have to say he is awesome ! So when I discovered this plugin a few days ago and when I realized who made it, I had to give it a try.

The bottom line about this plugin: If you know what you are doing, and follow his on screen instructions, this plugin is also awesome ! 

What makes me appreciate this developer even more is the fact that on the plugin's options screen he has a small non intrusive link asking for reviews, unlike some others who really turn you off with the constant nagging and begging, or even worse the inclusion of Freemium or other "spying" scripts.

Thanks a million Jeff,
Nick.

Works Perfectly !

Easily switch between themes for development and testing.

xhtmlweaver

In short, this plugin allows you to modify/switch the current theme with live site on the fly without messing up with your current visitors. 
This plugin is perfect for WordPress theme developers, freelancers as it allows you to edit the live theme without interfering the current visitors. 
It offers following features:
<ul>
<li>Ability to duplicate any current themes to the new theme for editing purpose.</li>
<li>Selectively enabling the theme switcher on the frontend by enabling extra settings in the backend. (By role or by IP Addresses)</li>
<li>Provides an Ajax theme switcher on the right top which selectively allows the visitor (by role or IP Addresses) to switch the theme.</li>
<li>A transparent banner on the top to display current theme.</li>
<li>Full Support is available at http://www.xhtmlweaver.com or wp-support@xhtmlweaver.com</li>
</ul>

Parallels Themes Switcher

This plugin allows you to modify/switch the current theme on the live site without interfering the current visitors.

Theme Switcha – Easily Switch Themes for Development and Testing vs Parallels Themes Switcher