There is a complete set of reserved keywords, or terms, in WordPress that should not be used in certain circumstances as they may conflict with core functionality. You should avoid using any of these terms when:

• Passing a term through a $_GET or $_POST array
• Registering a taxonomy or post type slug
• Handling query variables

For other possible variable conflicts, see Global Variables.

Reserved terms

• action
• attachment
• attachment_id
• author
• author_name
• calendar
• cat
• category
• category__and
• category__in
• category__not_in
• category_name
• comments_per_page
• comments_popup
• custom
• customize_messenger_channel
• customized
• cpage
• day
• debug
• embed
• error
• exact
• feed
• fields
• hour
• link_category
• m
• minute
• monthnum
• more
• name
• nav_menu
• nonce
• nopaging
• offset
• order
• orderby
• p
• page
• page_id
• paged
• pagename
• pb
• perm
• post
• post__in
• post__not_in
• post_format
• post_mime_type
• post_status
• post_tag
• post_type
• posts
• posts_per_archive_page
• posts_per_page
• preview
• robots
• s
• search
• second
• sentence
• showposts
• static
• status
• subpost
• subpost_id
• tag
• tag__and
• tag__in
• tag__not_in
• tag_id
• tag_slug__and
• tag_slug__in
• taxonomy
• tb
• term
• terms
• theme
• title
• type
• types
• w
• withcomments
• withoutcomments
• year

Reserved handle slugs

• about
• accordion
• admin-bar
• admin-bar
• admin-comments
• admin-gallery
• admin-menu
• admin-tags
• admin-widgets
• autosave
• backbone
• buttons
• clipboard
• code-editor
• code-editor
• colorpicker
• colors
• colors-fresh
• comment
• comment-reply
• common
• common
• cropper
• csslint
• custom-background
• custom-header
• custom-html-widgets
• customize-base
• customize-controls
• customize-controls
• customize-loader
• customize-models
• customize-nav-menus
• customize-nav-menus
• customize-preview
• customize-preview
• customize-preview-nav-menus
• customize-preview-widgets
• customize-selective-refresh
• customize-views
• customize-widgets
• customize-widgets
• dashboard
• dashboard
• dashicons
• deprecated-media
• edit
• editor
• editor-buttons
• editor-expand
• esprima
• farbtastic
• farbtastic
• forms
• handle
• heartbeat
• hoverIntent
• hoverintent-js
• htmlhint
• htmlhint-kses
• image-edit
• imagesloaded
• imgareaselect
• imgareaselect
• inline-edit-post
• inline-edit-tax
• install
• iris
• jcrop
• jcrop
• jquery
• jquery-color
• jquery-core
• jquery-effects-blind
• jquery-effects-bounce
• jquery-effects-clip
• jquery-effects-core
• jquery-effects-drop
• jquery-effects-explode
• jquery-effects-fade
• jquery-effects-fold
• jquery-effects-highlight
• jquery-effects-puff
• jquery-effects-pulsate
• jquery-effects-scale
• jquery-effects-shake
• jquery-effects-size
• jquery-effects-slide
• jquery-effects-transfer
• jquery-form
• jquery-hotkeys
• jquery-masonry
• jquery-migrate
• jquery-query
• jquery-serialize-object
• jquery-table-hotkeys
• jquery-touch-punch
• jquery-ui-accordion
• jquery-ui-autocomplete
• jquery-ui-button
• jquery-ui-core
• jquery-ui-datepicker
• jquery-ui-dialog
• jquery-ui-draggable
• jquery-ui-droppable
• jquery-ui-menu
• jquery-ui-mouse
• jquery-ui-position
• jquery-ui-progressbar
• jquery-ui-resizable
• jquery-ui-selectable
• jquery-ui-selectmenu
• jquery-ui-slider
• jquery-ui-sortable
• jquery-ui-spinner
• jquery-ui-tabs
• jquery-ui-tooltip
• jquery-ui-widget
• jshint
• json2
• jsonlint
• l10n
• language-chooser
• link
• list-revisions
• list-tables
• login
• masonry
• mce-view
• media
• media
• media-audio-widget
• media-audiovideo
• media-editor
• media-gallery
• media-gallery-widget
• media-grid
• media-image-widget
• media-models
• media-upload
• media-video-widget
• media-views
• media-views
• media-widgets
• mediaelement
• mediaelement
• mediaelement-core
• mediaelement-migrate
• mediaelement-vimeo
• moxiejs
• nav-menu
• nav-menus
• open-sans
• password-strength-meter
• plugin-install
• plupload
• plupload-handlers
• post
• postbox
• privacy-tools
• prototype
• quicktags
• revisions
• revisions
• sack
• schedule
• scriptaculous
• scriptaculous-builder
• scriptaculous-controls
• scriptaculous-dragdrop
• scriptaculous-effects
• scriptaculous-root
• scriptaculous-slider
• scriptaculous-sound
• set-post-thumbnail
• shortcode
• site-health
• site-health
• site-icon
• suggest
• svg-painter
• swfobject
• swfupload
• swfupload-all
• swfupload-handlers
• tags-box
• tags-suggest
• text-widgets
• theme
• themes
• thickbox
• thickbox
• underscore
• updates
• user-profile
• user-suggest
• utils
• widgets
• word-count
• wp-admin
• wp-ajax-response
• wp-api
• wp-api-request
• wp-auth-check
• wp-auth-check
• wp-backbone
• wp-block-library-theme
• wp-codemirror
• wp-codemirror
• wp-color-picker
• wp-color-picker
• wp-custom-header
• wp-edit-blocks
• wp-editor-font
• wp-embed
• wp-embed-template-ie
• wp-jquery-ui-dialog
• wp-lists
• wp-mediaelement
• wp-mediaelement
• wp-playlist
• wp-plupload
• wp-pointer
• wp-pointer
• wp-polyfill
• wp-sanitize
• wp-theme-plugin-editor
• wp-tinymce
• wp-tinymce
• wp-tinymce-lists
• wp-tinymce-root
• wp-util
• wpdialogs
• wplink
• xfn
• zxcvbn-async

Related

• WordPress_Query_Vars
• Global_Variables