On December 12, 2013, WordPress Version 3.8, named for Charlie Parker, was released to the public. For more information on this enhancement and bug-fix release, read the WordPress Blog, the Release Post, and see the Changelog for 3.8.

For Version 3.8, the database version (db_version in wp_options) changed to 26691, and the Trac revision was r26861.

Highlights

• Introduces a new, modern admin design
  • A fresh, uncluttered design
  • Clean typography with Open Sans
  • Superior contrast and large, comfortable type
  • Responsive interfaces throughout
  • Refined, theme management
  • Smoother, click-to-add widget management

• New Default Theme – Twenty Fourteen
  • Easily create a responsive magazine website with a sleek, modern design.
  • Feature your favorite homepage content in either a grid or a slider.
  • Use the three widget areas to customize your website, and change your content’s layout with a full-width page template and a contributor page to show off your authors.

• For Developers
  • External Libraries have been updated.
  • Better RTL support
  • Theme screenshots’ size have increased from 600 × 450 to 880 × 660.

What’s New

General

• Replace PNG-based plugins ratings stars with Dashicons for performance gains
• Improved help tab text in various screens
• Clicking “Check Again” on the Updates screen now provides more immediate feedback

Dashboard

• Consolidate several Dashboard widgets to improve readability
• Replace the ‘Right Now’ widget with the new and improved ‘At a Glance’ widget

Appearance

• Introduce 8 new admin color schemes
• Improved readability throughout using Open Sans typeface (where supported)
• Responsive Toolbar for smaller-screen devices
• Leverage Dashicons instead of icon sprites for crisper experience on all resolutions
• Big RTL improvements throughout
• Make the dashboard more usable on any size device with responsive all the things
• Improve the login screen experience for Internet Explorer 8 users
• Improve Quick Edit experience for non-English users
• Improve the Menus experience for mobile users

Themes

• New Default Theme — Twenty Fourteen
• Make it possible to check for any post format assigned to a post with has_post_format()
• Better custom background theme support defaults, can now specify ‘default-repeat’, ‘default-position-x’, and ‘default-attachment’ arguments for background images.
• Tags for width changed to layout: responsive-layout, fluid-layout, and fixed-layout
• New tag: accessibility-ready to denote a theme is aware of accessibility best practices such as color contrast, keyboard navigation, and form/link focus. See WP theme accessibility guidelines.

Widgets

• New click-to-add interface for adding widgets to sidebars
• Improved interface for devices of all resolutions
• Better drag-and-drop experience

Accessibility

• Make list table row actions keyboard accessible
• Improve color contrast throughout the admin

Multisite

• Improved performance when deleting users in Multisite

Under The Hood

General

• Heartbeat performance and API improvements
• A $taxonomy argument was added to each of the adjacent post functions.
• Define $is_nginx in vars.php
• Apply capital_P_dangit() to the wp_title filter
• Make sure ajaxurl is defined in the Customizer
• validate_active_plugins() now checks the manage_network_plugins capability instead of is_super_admin()
• Add a show_metabox parameter to register_taxonomy()
• Make it easier to target video shortcodes by adding a wp-video class to the parent container
• Add CSSMin, SASS, CSSJanus, and jsHint to build tools for core development

Bug Fixes

• Fix bug where top-level categories were only redirecting if they had no children
• Fix bug in wp_get_object_terms() where returned were strings not integers
• Fix a bug where passing a null value to meta_query resulted in wonkiness with the comparison operator
• Fix “‘wp_signups’ already exists for query” error after updating a Multisite network
• Fix bug in get_bookmarks() caused by missing parentheses
• Fix comment_notification_recipients filter behavior so that it is still respected even on comments left by the post author
• Fix a date comparison error in dashboard_relative_date()
• Fix keyboard accessibility for row actions in list tables.
• Fix no-js and accessibility modes in in the Widgets screen
• Fix a bug where menus could still be assigned to a non-existent theme location
• Silence jQuery Migrate errors in the General settings page

Multisite

Classes

• Introduce WP_Screen::remove_option()
• Introduce WP_Screen::remove_options()
• Introduce WP_Screen::get_options()

Functions

• Introduce wp_dashboard_quick_press()
• Introduce wp_dashboard_site_activity()
• Introduce wp_dashboard_recent_posts()
• Introduce wp_dashboard_recent_comments()
• Introduce wp_dashboard_primary_output()
• Introduce wp_heartbeat_set_suspension()
• Introduce wp_star_rating()
• Introduce get_theme_update_available()
• Introduce wp_prepare_themes_for_js()

Actions & Filters

Actions

• Introduce automatic_updates_complete

Filters

• Introduce automatic_updates_debug_email
• Introduce wp_prepare_themes_for_js

External Libraries

• Add a copyright notice to zxcvbn (password strength meter) script

Deprecated

• screen_icon()
• get_screen_icon()
• wp_dashboard_incoming_links_output()
• wp_dashboard_secondary_output()
• wp_dashboard_incoming_links()
• wp_dashboard_incoming_links_control()
• wp_dashboard_plugins()
• wp_dashboard_primary_control()
• wp_dashboard_recent_comments_control()
• wp_dashboard_secondary()
• wp_dashboard_secondary_control()
• no_update_actions()

Miscellaneous

• Many unused images were removed from core. See the full list