The Theme Check plugin, created by the WordPress.org team, can be used to perform a preliminary check to see whether your themes are compatible with ThemeSwitcher Pro.

In particular, themes that register custom post types and taxonomies will not be compatible with ThemeSwitcher Pro. It’s a best practice to register custom post types and taxonomies using a plugin. Moving and custom post type or taxonomy registration code into a plugin will help to ensure that your theme is compatible with ThemeSwitcher Pro.

To check a theme using the Theme Check plugin, activate the plugin, then view the settings page by navigating to Dashboard > Appearance > Theme Check.

Select the theme to test, then click the “Check it!” button.

The Theme Check plugin runs various tests to check if a theme is ready for consideration for being added to the WordPress.org theme repository, but we’re only concerned with the checks for register_post_type() and register_taxonomy(). If your theme fails either of these checks, you will see the following results after the scan.

If these checks fail, and you have a custom theme, you can move the post type and taxonomy registration code out of the theme and into a plugin. This process is beyond the scope of this document, but it should be straight-forward for a developer to do this. Once the post type and/or taxonomy registration code has been moved to a plugin, the theme will likely be compatible with ThemeSwitcher Pro.