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To change a WordPress theme safely, open Appearance > Themes, preview the candidate with your existing site content, and activate it only after checking that the preview displays properly. After activation, review important pages, navigation, and widgets. The editing controls differ between classic and block themes, so identify which type you are using before making adjustments.
1. Identify the theme type and its editing controls
Classic themes commonly provide Appearance > Customize, along with separate menu and widget controls where supported. Block themes use the Site Editor to work on site areas such as navigation, the header, content, and footer. The Customizer is available only when the active theme supports it.
| What to check | Classic theme | Block theme |
|---|---|---|
| Main editing interface | Customizer, where supported; often separate menu and widget controls | Site Editor for site areas and navigation |
| Site areas | Templates, widget areas, and menu locations vary by theme | Blocks can be used for navigation, header, content, and footer |
| Preview and testing | Customizer live preview and theme preview | Live Preview in the Site Editor; a test site may help with fuller evaluation |
| Post-switch checks | Confirm menu locations and widget areas | Check navigation, templates, and template parts in the Site Editor |
2. Find or install the theme you want
In the dashboard, go to Appearance > Themes. To browse the official WordPress Theme Directory, choose Add New; you can search for a theme, preview it, and install it. If you already have a theme file, upload it as a ZIP file from the Themes screen. Themes already installed on your site can also be previewed there before activation.
3. Preview the candidate before activating it
Use the theme preview with your site’s existing content. Check representative pages and, when the interface offers them, desktop, tablet, and mobile previews. Look for problems with page layouts, navigation, or other visible site areas.
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If the preview is blank, investigate instead of activating the theme immediately: WordPress warns that a blank preview may indicate the site will not display correctly. For a more extensive evaluation of a block theme, consider trying it on a test site before using it on a live site.
4. Activate the theme and check the site
When the preview looks right, activate the selected theme from the Themes screen. Then visit important pages and check that the navigation and site areas appear as expected. Use the controls for the theme type you are running:
- Classic theme: check the theme’s available menu locations and widget areas.
- Block theme: use the Site Editor to review navigation and site areas, including templates and template parts.
5. Look for widgets that moved
Widget areas can differ between themes, including their number and placement. If a widget is no longer visible after the switch, check Inactive Widgets before assuming it was deleted. WordPress may retain the previous widget arrangement and settings there after a theme change.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.6. Treat deleting the old theme as a separate decision
Activating a new theme does not mean you must immediately delete the previous one. Deleting a theme removes its files and any customizations made in those files. WordPress advises considering a backup before deletion.
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