Last checked and updated on April 20, 2026What Is New in WordPress 3.9
WordPress 3.9, "Smith", brings significant improvements to the visual editor, media management, and theme customization experience.
| Category | Key Changes |
|---|---|
| New Features | Live widget previews, updated visual editor, new gallery preview |
| Improvements | Drag-and-drop images, audio/video playlists, editor scrolling |
| Theme Features | Header video, theme browser improvements |
| Under the Hood | Updated libraries, improved database layer |
How did the visual editor improve in 3.9?
The TinyMCE editor was updated to version 4.0, which fixed a ton of long-standing bugs and modernized the entire editing experience. You'll notice the editor no longer scrolls away when adding images or switching between Visual and Text tabs. In practice, this makes writing and formatting content feel much more stable and fluid.
Pasting content from Microsoft Word or other external sources is now much cleaner. The editor does a better job of stripping out the weird, non-standard formatting that used to break site layouts.
What changed with media management?
Media handling got a major usability boost. You can now drag and drop images directly into the editor, and they'll upload and embed automatically. The media modal was redesigned to be more intuitive, showing a grid of your media library.
Galleries now show a live preview right in the editor instead of just a placeholder shortcode. This is a huge time-saver because you can immediately see what your image collection will look like without having to save and preview the post.
Were there updates for theme developers?
Absolutely. The theme customizer was enhanced with live widget previews. You can now add, edit, and rearrange widgets directly in the customizer and see the changes happen in real-time on your site preview. This matters because it removes the guesswork from widget management for clients and site builders.
The theme installation process was also improved. The new theme browser provides a better visual experience with larger previews and smoother navigation when searching for and installing new themes.
What about audio and video features?
Audio and video playlists were introduced in this release. You can now create simple, embedded playlists by selecting multiple audio or video files from your media library. This was a highly requested feature for musicians, podcasters, and anyone managing media-rich content.
The update also improved the overall handling of embedded content, making it more reliable to embed videos from services like YouTube and Vimeo directly into posts and pages.
What happened under the hood?
Several core libraries were updated. jQuery was bumped to version 1.11.1, and jQuery UI to 1.10.4, bringing performance improvements and bug fixes. The database layer saw optimizations for handling serialized data, which improves reliability.
For developers, there were new functions and hooks added. The wp_get_theme() function became more robust, providing better information about the current theme and its parent, if it's a child theme.
FAQ
Does the new TinyMCE 4.0 editor break any plugins that add buttons to the toolbar?
It might. While the API is largely the same, some older plugins that added custom buttons may need to be updated to be fully compatible with the new TinyMCE version. It's a good idea to test your essential plugins after upgrading.
How do the new live widget previews work in the customizer?
They use the same JavaScript APIs as the rest of the customizer. When you add or modify a widget, the changes are instantly reflected in the preview pane without requiring a full page reload, making the setup process much faster.
Is there a new method for creating image galleries?
The process is the same, but the output is different. You still create a gallery by selecting multiple images, but instead of inserting a simple shortcode, the editor now renders an actual preview of the image grid, giving you a much better idea of the final result.
Were any security issues addressed in this release?
Yes, WordPress 3.9 included multiple security fixes. While the details are typically kept vague to prevent exploitation, it's always recommended to upgrade promptly to ensure your site is protected against known vulnerabilities.
Can I use header videos with any theme?
No, header video support is a theme feature. Themes need to explicitly add support for it using add_theme_support( 'custom-header', array( 'video' => true ) ). The Twenty Fourteen theme included with WordPress 3.9 was updated to support this feature.