WordPress constants overview

In the backend of WordPress you don’t have an input field for each possible modification. Some are only available via an action or a filter and for some changes you need to define or change a PHP constant.
In this article I have listed all constants which WordPress has by nature (except the deprecated ones).

A constant is an identifier (name) for a simple value. As the name suggests, that value cannot change during the execution of the script. A constant is case-sensitive by default. By convention, constant identifiers are always uppercase.
PHP docs

Content

• General
• Status
• Paths, dirs and links
• Database
• Multisite
• Cache and script compressing
• Filesystem and connections
• Themes
• Debug
• Security and cookies

General

• AUTOSAVE_INTERVAL #
  Defines an interval, in which WordPress should do an autosave.
  Value: time in seconds (Default: 60)
• CORE_UPGRADE_SKIP_NEW_BUNDLED #
  Allows you to skip new bundles files like plugins and/or themes on upgrades.
  Values: true|false
• DISABLE_WP_CRON #
  Deactivates the cron function of WordPress.
  Value: true
• EMPTY_TRASH_DAYS #
  Controls the number of days before WordPress permanently deletes posts, pages, attachments, and comments, from the trash bin.
  Value: time in days (Default: 30)
• IMAGE_EDIT_OVERWRITE #
  Allows WordPress to override an image after editing or to save the image as a copy.
  Values: true|false
• MEDIA_TRASH #
  (De)activates the trash bin function for media.
  Values: true|false (Default: false)
• WPLANG #
  Defines the language which WordPress should use.
  Values: For German de_DE
• WP_DEFAULT_THEME #
  Defines a default theme for new sites, also used as fallback for a broken theme.
  Value: template name (Default: twentyeleven)
• WP_CRON_LOCK_TIMEOUT #
  Defines a period of time in which only one cronjob will be fired. Since WordPress 3.3.
  Value: time in seconds (Default: 60)
• WP_MAIL_INTERVAL #
  Defines a period of time in which only one mail request can be done.
  Value: time in seconds (Default: 300)
• WP_POST_REVISIONS #
  (De)activates the revision function for posts. A number greater than 0 defines the number of revisions for one post.
  Values: true|false|number (Default: true)
• WP_MAX_MEMORY_LIMIT #
  Allows you to change the maximum memory limit for some WordPress functions.
  Values: See PHP docs (Default: 256M)
• WP_MEMORY_LIMIT #
  Defines the memory limit for WordPress.
  Values: See PHP docs (Default: 32M, for Multisite 64M)

Status

• APP_REQUEST #
  Will be defined if it’s an Atom Publishing Protocol request.
  Value: true
• COMMENTS_TEMPLATE #
  Will be defined if the comments template is loaded.
  Value: true
• DOING_AJAX #
  Will be defined if it’s an AJAX request.
  Value: true
• DOING_AUTOSAVE #
  Will be defined if WordPress is doing an autosave for posts.
  Value: true
• DOING_CRON #
  Will be defined if WordPress is doing a cronjob.
  Value: true
• IFRAME_REQUEST #
  Will be defined if it’s an inlineframe request.
  Value: true
• IS_PROFILE_PAGE #
  Will be defined if a user change his profile settings.
  Value: true
• SHORTINIT #
  Can be defined to load only the half of WordPress.
  Value: true
• WP_ADMIN #
  Will be defined if it’s a request in backend of WordPress.
  Value: true
• WP_BLOG_ADMIN #
  Will be defined if it’s a request in /wp-admin/.
  Value: true
• WP_IMPORTING #
  Will be defined if WordPress is importing data.
  Value: true
• WP_INSTALLING #
  Will be defined on an new installation or on an upgrade.
  Value: true
• #WP_INSTALLING_NETWORK #
  Will be defined if it’s a request in network admin or on installing a network. Since WordPress 3.3, previous WP_NETWORK_ADMIN_PAGE.
  Value: true
• WP_LOAD_IMPORTERS #
  Will be defined if you visit the importer overview (Tools → Importer).
  Value: true
• WP_NETWORK_ADMIN #
  Will be defined if it’s a request in /wp-admin/network/.
  Value: true
• WP_REPAIRING #
  Will be defined if it’s a request to /wp-admin/maint/repair.php.
  Value: true
• WP_SETUP_CONFIG #
  Will be defined if WordPress will be installed or configured.
  Value: true
• WP_UNINSTALL_PLUGIN #
  Will be defined if a plugin wil be uninstalled (for uninstall.php).
  Value: true
• WP_USER_ADMIN #
  Will be defined if it’s a request in /wp-admin/user/.
  Value: true
• XMLRPC_REQUEST #
  Will be defined if it’s a request over the XML-RPC API.
  Value: true

Paths, dirs and links

• ABSPATH #
  Absolute path to the WordPress root dir.
  Default: path to wp-load.php
• WPINC #
  Relative path to the /wp-includes/. You can’t change it.
  Default: wp-includes
• WP_LANG_DIR #
  Absolute path to the folder with language files.
  Default: WP_CONTENT_DIR /languages or WP_CONTENT_DIR WPINC /languages
• WP_PLUGIN_DIR #
  Absolute path to the plugins dir.
  Default: WP_CONTENT_DIR /plugins
• WP_PLUGIN_URL #
  URL to the plugins dir.
  Default: WP_CONTENT_URL /plugins
• WP_CONTENT_DIR #
  Absolute path to thewp-content dir.
  Default: ABSPATH wp-content
• WP_CONTENT_URL #
  URL to the wp-content dir.
  Default: {Site URL}/wp-content
• WP_HOME #
  Home URL of your WordPress.
• WP_SITEURL #
  URL to the WordPress root dir.
• WP_TEMP_DIR #
  Absolute path to a dir, where temporary files can be saved.
• WPMU_PLUGIN_DIR #
  Absolute path to the must use plugin dir.
  Default: WP_CONTENT_DIR /mu-plugins
• WPMU_PLUGIN_URL #
  URL to the must use plugin dir.
  Default: WP_CONTENT_URL /mu-plugins

Database

• DB_CHARSET #
  Defines the database charset.
  Values: See MySQL docs (Default: utf8)
• DB_COLLATE #
  Defines the database collation.
  Values: See MySQL docs (Default: utf8_general_ci)
• DB_HOST #
  Defines the database host.
  Values: IP address, domain and/or port (Default: localhost)
• DB_NAME #
  Defines the database name.
  Value: database name
• DB_PASSWORD #
  Defines the database password.
• DB_USER #
  Defines the database user.
• WP_ALLOW_REPAIR #
  Allows you to automatically repair and optimize the database tables via /wp-admin/maint/repair.php.
  Value: true
• CUSTOM_USER_TABLE #
  Allows you to define a custom user table.
  Value: table name
• CUSTOM_USER_META_TABLE #
  Allows you to define a custom user meta table.
  Value: table name

Multisite

• ALLOW_SUBDIRECTORY_INSTALL #
  Allows you to install Multisite in a subdirectory.
  Value: true
• BLOGUPLOADDIR #
  Absolute path to the site specific upload dir.
  Default: WP_CONTENT_DIR /blogs.dir/{Blog ID}/files/
• BLOG_ID_CURRENT_SITE #
  Blog ID of the main site.
  Default: 1
• DOMAIN_CURRENT_SITE #
  Domain of the main site.
  Default: domain
• DIEONDBERROR #
  When defined database errors will be displayed on screen.
  Value: true
• ERRORLOGFILE #
  When defined database erros will be logged into a file.
  Value: absolute path to a writeable file
• MULTISITE #
  Will be defined if Multisite is used.
  Value: true
• NOBLOGREDIRECT #
  Defines an URL of a site on which WordPress should redirect, if registration is closed or a site doesn’t exists.
  Values: %siteurl% for mainsite or custom URL
• PATH_CURRENT_SITE #
  Path to the main site.
• UPLOADBLOGSDIR #
  Path to the upload base dir, relative to ABSPATH.
  Default: wp-content/blogs.dir
• SITE_ID_CURRENT_SITE #
  Network ID of the main site.
  Default: 1
• SUBDOMAIN_INSTALL #
  Defines if it’s a subdomain install or not.
  Values: true|false
• SUNRISE #
  When defined WordPres will load the /wp-content/sunrise.php file.
  Value: true
• UPLOADS #
  Path to site specific upload dir, relative to ABSPATH.
  Default: UPLOADBLOGSDIR /{blogid}/files/
• WPMU_ACCEL_REDIRECT #
  (De)activates support for X-Sendfile Header.
  Values: true|false (Default: false)
• WPMU_SENDFILE #
  (De)activates support for X-Accel-Redirect Header.
  Values: true|false (Default: false)
• WP_ALLOW_MULTISITE #
  When defined the multisite function will be accessible (Tools → Network Setup).
  Value: true

Cache and script compressing

• WP_CACHE #
  When defined WordPres will load the /wp-content/advanced-cache.php file.
  Values: true|false (Default: false)
• COMPRESS_CSS #
  (De)activates the compressing of stylesheets.
  Values: true|false
• COMPRESS_SCRIPTS #
  (De)activates the compressing of Javascript files.
  Values: true|false
• CONCATENATE_SCRIPTS #
  (De)activates the consolidation of Javascript or CSS files before compressing.
  Values: true|false
• ENFORCE_GZIP #
  (De)activates gzip output.
  Values: true|false

Filesystem and connections

• FS_CHMOD_DIR #
  Defines the read and write permissions for directories.
  Values: See PHP handbook (Default: 0755)
• FS_CHMOD_FILE #
  Defines the read and write permissions for files.
  Values: See PHP handbook (Default: 0644)
• FS_CONNECT_TIMEOUT #
  Defines a timeout for building a connection.
  Values: time in seconds (Default: 30)
• FS_METHOD #
  Defines the method to connect to the filesystem.
  Values: direct|ssh|ftpext|ftpsockets
• FS_TIMEOUT #
  Defines a timeout after a connection has been lost.
  Values: time in seconds (Default: 30)
• FTP_BASE #
  Path to the WordPress root dir.
  Default: ABSPATH
• FTP_CONTENT_DIR #
  Path to the /wp-content/ dir.
  Default: WP_CONTENT_DIR
• FTP_HOST #
  Defines the FTP host.
  Values: IP Adresse, Domain und/oder Port
• FTP_LANG_DIR #
  Path to the folder with language files.
  Default: WP_LANG_DIR
• FTP_PASS #
  Defines the FTP password.
• FTP_PLUGIN_DIR #
  Path to the plugin dir.
  Default: WP_PLUGIN_DIR
• FTP_PRIKEY #
  Defines a private key for SSH.
• FTP_PUBKEY #
  Defines a public key for SSH.
• FTP_SSH #
  (De)activates SSH.
  Values: true|false
• FTP_SSL #
  (De)activates SSL.
  Values: true|false
• FTP_USER #
  Defines the FTP username.
• WP_PROXY_BYPASS_HOSTS #
  Allows you to define some adresses which shouldn’t be passed through a proxy.
  Values: www.example.com, *.example.org
• WP_PROXY_HOST #
  Defines the proxy adresse.
  Values: IP address or domain
• WP_PROXY_PASSWORD #
  Defines the proxy password.
• WP_PROXY_PORT #
  Defines the proxy port.
• WP_PROXY_USERNAME #
  Defines the proxy username.
• WP_HTTP_BLOCK_EXTERNAL #
  Allows you to block external request.
  Values: true|false
• WP_ACCESSIBLE_HOSTS #
  If WP_HTTP_BLOCK_EXTERNAL is defined you can add hosts which shouldn’t be blocked.
  Values: www.example.com, *.example.org

Themes

• BACKGROUND_IMAGE #
  Defines a default background image.
• HEADER_IMAGE #
  Defines a default header image.
• HEADER_IMAGE_HEIGHT #
  Defines the height of the header image.
• HEADER_IMAGE_WIDTH #
  Defines the width of the header image.
• HEADER_TEXTCOLOR #
  Defines the font color for the header text.
• NO_HEADER_TEXT #
  (De)activates the support for header text.
  Values: true|false
• STYLESHEETPATH #
  Defines the absolute path to the stylesheet of the current theme.
• TEMPLATEPATH #
  Defines the absolute path to the template files of the current theme.
• WP_USE_THEMES #
  (De)activates the loading of themes.
  Values: true|false

Debug

• SAVEQUERIES #
  (De)activates the saving of database queries in an array ($wpdb->queries).
  Values: true|false
• SCRIPT_DEBUG #
  (De)activates the loading of compressed Javascript and CSS files.
  Values: true|false
• WP_DEBUG #
  (De)activates the debug mode in WordPress.
  Values: true|false (Default: false)
• WP_DEBUG_DISPLAY #
  (De)activates the display of errors on the screen.
  Values: true|false|null (Default: true)
• WP_DEBUG_LOG #
  (De)activates the writing of errors to the /wp-content/debug.log file.
  Values: true|false (Default: false)

Security and cookies

• ADMIN_COOKIE_PATH #
  Path to the /wp-admin/ dir.
  Default: SITECOOKIEPATH wp-admin or for Multisite in subdirectory SITECOOKIEPATH
• ALLOW_UNFILTERED_UPLOADS #
  Allows unfiltered uploads by admins.
  Value: true
• AUTH_COOKIE #
  Cookie name for the authentication.
  Default: wordpress_ COOKIEHASH
• AUTH_KEY #
  Secret key.
  Values: See generator
• AUTH_SALT #
  Secret key.
  Values: See generator
• COOKIEHASH #
  Hash for generating cookie names.
• COOKIEPATH #
  Path to WordPress root dir.
  Default: Home URL without http(s)://
• COOKIE_DOMAIN #
  Domain of the WordPress installation.
  Default: false or for Multisite with subdomains .domain of the main site
• CUSTOM_TAGS #
  Allows you to override the list of secure HTML tags. See /wp-includes/kses.php.
  Values: true|false (Default: false)
• DISALLOW_FILE_EDIT #
  Allows you to disallow theme and plugin edits via WordPress editor.
  Value: true
• DISALLOW_FILE_MODS #
  Allows you to disallow the editing, updating, installing and deleting of plugins, themes and core files via WordPress Backend.
  Value: true
• DISALLOW_UNFILTERED_HTML #
  Allows you to disallow unfiltered HTML for every user, admins too.
  Value: true
• FORCE_SSL_ADMIN #
  Activates SSL for logins and in the backend.
  Values: true|false (Default: false)
• FORCE_SSL_LOGIN #
  Activates SSL for logins.
  Values: true|false (Default: false)
• LOGGED_IN_COOKIE #
  Cookie name for logins.
  Default: wordpress_logged_in_ COOKIEHASH
• LOGGED_IN_KEY #
  Secret key.
  Values: See generator
• LOGGED_IN_SALT #
  Secret key.
  Values: See generator
• NONCE_KEY #
  Secret key.
  Values: See generator
• NONCE_SALT #
  Secret key.
  Values: See generator
• PASS_COOKIE #
  Cookie name for the password.
  Default: wordpresspass_ COOKIEHASH
• PLUGINS_COOKIE_PATH #
  Path to the plugins dir.
  Default: WP_PLUGIN_URL without http(s)://
• SECURE_AUTH_COOKIE #
  Cookie name for the SSL authentication.
  Default: wordpress_sec_ COOKIEHASH
• SECURE_AUTH_KEY #
  Secret key.
  Values: See generator
• SECURE_AUTH_SALT #
  Secret key.
  Values: See generator
• SITECOOKIEPATH #
  Path of you site.
  Default: Site URL without http(s)://
• TEST_COOKIE #
  Cookie name for the test cookie.
  Default: wordpress_test_cookie
• USER_COOKIE #
  Cookie name for users.
  Default: wordpressuser_ COOKIEHASH