Actions let you execute code at specific points in WordPress. They don’t return values — they fire and trigger side effects.
add_action( $hook, $callback, $priority, $args )
wp_headOutputs content in the <head> section
wp_head is the print slot inside document head. Use it for meta tags and inline snippets — not for enqueueing CSS or JS files.
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do_action( 'wp_head' );Example
add_action( 'wp_head', function() {
echo '<meta name="theme-color" content="#0073aa">';
} );Common Use Cases
wp_footerFires before </body> closing tag
wp_footer is the last print slot on the front-end. Deferred scripts, analytics, and widgets that must load after content belong here.
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do_action( 'wp_footer' );Example
add_action( 'wp_footer', function() {
echo '<script>console.log("Footer loaded");</script>';
} );Common Use Cases
initRuns after WordPress has finished loading
init is the default place to register post types, taxonomies, and rewrite-related APIs. It fires after plugins are loaded and before headers go out.
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do_action( 'init' );Example
add_action( 'init', function() {
register_post_type( 'book', [
'public' => true,
'label' => 'Books',
] );
} );Common Use Cases
wp_enqueue_scriptsThe correct hook to enqueue frontend assets
Queue front-end CSS and JS here. WordPress prints the tags during wp_head / wp_footer — do not echo link or script tags yourself.
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do_action( 'wp_enqueue_scripts' );Example
add_action( 'wp_enqueue_scripts', function() {
wp_enqueue_style( 'my-style', get_stylesheet_uri() );
wp_enqueue_script( 'my-script', get_template_directory_uri() . '/js/main.js', [], '1.0', true );
} );Common Use Cases
save_postFires after a post is saved or updated
save_post runs after WordPress writes the post row. Use it for caches, sync, and derived data — and always guard against autosave, revisions, and infinite loops.
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do_action( 'save_post', int $post_id, WP_Post $post, bool $update );Example
add_action( 'save_post', function( $post_id, $post ) {
if ( $post->post_type !== 'book' ) {
return;
}
delete_transient( 'book_list_' . $post_id );
}, 10, 2 );Common Use Cases
admin_initFires at the beginning of every admin page
admin_init is the admin counterpart to init: settings, redirects, and capability checks that must not run on the front-end.
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do_action( 'admin_init' );Example
add_action( 'admin_init', function() {
register_setting( 'my_options_group', 'my_option_name' );
} );Common Use Cases
plugins_loadedFires once all active plugins have loaded
plugins_loaded is the earliest point where every active plugin's functions and classes are guaranteed to exist — use it for cross-plugin checks, not for registering WordPress objects.
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do_action( 'plugins_loaded' );Example
add_action( 'plugins_loaded', function() {
if ( class_exists( 'WooCommerce' ) ) {
require_once __DIR__ . '/integrations/woocommerce.php';
}
} );Common Use Cases
wp_loadedFires once WordPress, plugins, and theme are fully loaded
wp_loaded runs after every init callback has finished — use it when your code depends on things other plugins register on init.
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do_action( 'wp_loaded' );Example
add_action( 'wp_loaded', function() {
if ( ! post_type_exists( 'book' ) ) {
return;
}
flush_rewrite_rules();
} );Common Use Cases
after_setup_themeFires after the theme is loaded, before init
after_setup_theme is where themes declare support for core features — post thumbnails, menus, HTML5 markup — before WordPress finishes bootstrapping.
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do_action( 'after_setup_theme' );Example
add_action( 'after_setup_theme', function() {
add_theme_support( 'post-thumbnails' );
add_theme_support( 'title-tag' );
register_nav_menus( [ 'primary' => 'Primary Menu' ] );
} );Common Use Cases
widgets_initFires when it's time to register widgets and sidebars
widgets_init is exclusively for register_sidebar() and register_widget() calls — nothing else belongs here.
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do_action( 'widgets_init' );Example
add_action( 'widgets_init', function() {
register_sidebar( [
'name' => 'Footer Widgets',
'id' => 'footer-widgets',
'before_widget' => '<div class="widget %2$s">',
'after_widget' => '</div>',
] );
} );Common Use Cases
admin_enqueue_scriptsThe correct hook to enqueue admin-only assets
admin_enqueue_scripts is the admin equivalent of wp_enqueue_scripts — always check $hook_suffix so you don't load your CSS/JS on every admin screen.
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do_action( 'admin_enqueue_scripts', string $hook_suffix );Example
add_action( 'admin_enqueue_scripts', function( $hook_suffix ) {
if ( 'post.php' !== $hook_suffix ) {
return;
}
wp_enqueue_script( 'my-admin-js', plugins_url( 'admin.js', __FILE__ ), [ 'jquery' ], '1.0', true );
} );Common Use Cases
template_redirectFires right before WordPress decides which template to load
template_redirect is the standard place to short-circuit a request — custom redirects, maintenance mode, or blocking access — after the query is known but before any template file loads.
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do_action( 'template_redirect' );Example
add_action( 'template_redirect', function() {
if ( is_page( 'old-page' ) ) {
wp_safe_redirect( home_url( '/new-page/' ), 301 );
exit;
}
} );Common Use Cases
pre_get_postsModify any WP_Query before it runs
pre_get_posts fires for every query — main and secondary. Always check is_main_query() (and is_admin()) or you'll silently break widgets, related-post queries, and REST requests.
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do_action( 'pre_get_posts', WP_Query $query );Example
add_action( 'pre_get_posts', function( $query ) {
if ( ! is_admin() && $query->is_main_query() && is_post_type_archive( 'book' ) ) {
$query->set( 'posts_per_page', 24 );
}
} );Common Use Cases
wp_insert_postFires immediately after a post is inserted or updated in the database
wp_insert_post looks like save_post but fires from every wp_insert_post() call, including programmatic inserts that never touch the block editor.
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do_action( 'wp_insert_post', int $post_id, WP_Post $post, bool $update );Example
add_action( 'wp_insert_post', function( $post_id, $post, $update ) {
if ( 'book' !== $post->post_type || $update ) {
return;
}
wp_mail( get_option( 'admin_email' ), 'New book added', get_the_title( $post_id ) );
}, 10, 3 );Common Use Cases
transition_post_statusFires whenever a post's status changes
transition_post_status is the only hook that reliably tells you a status changed — including the old value — which save_post cannot do.
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do_action( 'transition_post_status', string $new_status, string $old_status, WP_Post $post );Example
add_action( 'transition_post_status', function( $new_status, $old_status, $post ) {
if ( 'publish' === $new_status && 'publish' !== $old_status ) {
wp_mail( get_option( 'admin_email' ), 'Post published', get_the_title( $post ) );
}
}, 10, 3 );Common Use Cases
admin_menuFires before the admin menu is rendered — register menu pages here
admin_menu is exclusively for add_menu_page() / add_submenu_page() calls; anything else belongs on admin_init.
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do_action( 'admin_menu' );Example
add_action( 'admin_menu', function() {
add_menu_page( 'My Plugin', 'My Plugin', 'manage_options', 'my-plugin', 'my_plugin_render_page', 'dashicons-admin-generic', 66 );
} );Common Use Cases
admin_noticesFires to print admin notices at the top of admin pages
admin_notices runs on every admin screen — always check current_user_can() or a specific screen ID so your notice doesn't nag every user on every page.
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do_action( 'admin_notices' );Example
add_action( 'admin_notices', function() {
if ( ! current_user_can( 'manage_options' ) ) {
return;
}
echo '<div class="notice notice-warning"><p>Please configure My Plugin.</p></div>';
} );Common Use Cases
wp_loginFires after a user has successfully logged in
wp_login fires only on a successful authentication — pair it with wp_login_failed to cover both outcomes.
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do_action( 'wp_login', string $user_login, WP_User $user );Example
add_action( 'wp_login', function( $user_login, $user ) {
update_user_meta( $user->ID, 'last_login', current_time( 'mysql' ) );
}, 10, 2 );Common Use Cases
user_registerFires immediately after a new user is registered
user_register fires right after wp_insert_user() writes the row — the account exists but you're still inside the registration request, which matters for redirects and emails.
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do_action( 'user_register', int $user_id, array $userdata );Example
add_action( 'user_register', function( $user_id ) {
$user = new WP_User( $user_id );
$user->set_role( 'subscriber' );
wp_mail( $user->user_email, 'Welcome!', 'Thanks for registering.' );
} );Common Use Cases
rest_api_initFires when the REST API is initialized — register custom routes here
rest_api_init is the register_rest_route() equivalent of init — it only fires on REST requests, not every page load.
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do_action( 'rest_api_init', WP_REST_Server $wp_rest_server );Example
add_action( 'rest_api_init', function() {
register_rest_route( 'my-plugin/v1', '/books', [
'methods' => 'GET',
'callback' => 'my_plugin_get_books',
'permission_callback' => '__return_true',
] );
} );Common Use Cases
wp_logoutFires after a user logs out
wp_logout is the mirror of wp_login — use it to clear per-user cookies, caches, or add custom redirect logic.
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do_action( 'wp_logout', int $user_id );Example
add_action( 'wp_logout', function( $user_id ) {
delete_transient( 'user_session_' . $user_id );
} );Common Use Cases
comment_postFires immediately after a comment is inserted
comment_post fires right after a new comment saves — the standard place to trigger notifications or moderation logic.
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do_action( 'comment_post', int $comment_id, int|string $comment_approved, array $comment_data );Example
add_action( 'comment_post', function( $comment_id, $approved ) {
if ( 1 === $approved ) {
wp_mail( get_option( 'admin_email' ), 'New comment', 'A comment was just approved.' );
}
}, 10, 2 );Common Use Cases
wp_insert_commentFires right after a comment row is written to the database
wp_insert_comment is the lower-level sibling of comment_post — it fires for every comment insert, including ones triggered programmatically, not just front-end submissions.
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do_action( 'wp_insert_comment', int $id, WP_Comment $comment );Example
add_action( 'wp_insert_comment', function( $id, $comment ) {
error_log( 'New comment #' . $id . ' on post ' . $comment->comment_post_ID );
}, 10, 2 );Common Use Cases
enqueue_block_editor_assetsLoads scripts/styles inside the block editor only
enqueue_block_editor_assets is the block-editor-only counterpart to wp_enqueue_scripts — it never runs on the public front-end.
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do_action( 'enqueue_block_editor_assets' );Example
add_action( 'enqueue_block_editor_assets', function() {
wp_enqueue_script(
'my-block-editor-script',
get_template_directory_uri() . '/js/editor.js',
[ 'wp-blocks', 'wp-element', 'wp-editor' ],
'1.0'
);
} );Common Use Cases
before_delete_postFires right before a post is permanently deleted
before_delete_post is your last chance to act while the post (and its data) still exists — right after this, wp_delete_post() removes the row for good.
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do_action( 'before_delete_post', int $post_id, WP_Post $post );Example
add_action( 'before_delete_post', function( $post_id, $post ) {
if ( 'book' !== $post->post_type ) {
return;
}
global $wpdb;
$wpdb->delete( $wpdb->prefix . 'book_ratings', [ 'post_id' => $post_id ] );
}, 10, 2 );Common Use Cases
enqueue_block_assetsLoads scripts/styles in both the block editor and the front-end
enqueue_block_assets is the one enqueue hook that runs in both places — the block editor and the public front-end — making it the right spot for a block's own shared styling.
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do_action( 'enqueue_block_assets' );Example
add_action( 'enqueue_block_assets', function() {
wp_enqueue_style( 'my-block-style', get_template_directory_uri() . '/css/block.css' );
} );Common Use Cases
Filters let you modify data before WordPress uses or displays it. They always receive a value and must return it (modified or not).
apply_filters( $hook, $value, …$args )
the_contentFilters post content before display
the_content is the last chance to change post HTML before it reaches the template. Always return the string — filters that echo will break the page.
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apply_filters( 'the_content', string $content );Example
add_filter( 'the_content', function( $content ) {
if ( is_single() ) {
$content .= '<p><strong>Thanks for reading!</strong></p>';
}
return $content;
} );Common Use Cases
the_titleFilters the post title
the_title changes how a title is displayed, not the value in the database. Guard with post ID so menus and admin lists are not rewritten by accident.
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apply_filters( 'the_title', string $title, int $id );Example
add_filter( 'the_title', function( $title, $id ) {
if ( get_post_type( $id ) === 'book' ) {
return 'Book: ' . $title;
}
return $title;
}, 10, 2 );Common Use Cases
wp_titleFilters the document <title> tag
wp_title is the classic document-title filter. Modern themes should prefer document_title_parts — this hook remains for older title tags.
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apply_filters( 'wp_title', string $title, string $sep, string $seplocation );Example
add_filter( 'wp_title', function( $title, $sep ) {
return $title . $sep . get_bloginfo( 'name' );
}, 10, 2 );Common Use Cases
body_classFilters the CSS classes on <body>
body_class lets CSS target context without extra wrappers. Return the array — do not echo class names.
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apply_filters( 'body_class', string[] $classes, string[] $css_class );Example
add_filter( 'body_class', function( $classes ) {
if ( is_user_logged_in() ) {
$classes[] = 'user-logged-in';
}
return $classes;
} );Common Use Cases
excerpt_lengthControls the auto-generated excerpt word count
excerpt_length only affects auto excerpts, not the Excerpt box in the editor. Return an integer word count.
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apply_filters( 'excerpt_length', int $number );Example
add_filter( 'excerpt_length', function( $length ) {
return 30;
} );Common Use Cases
login_urlFilters the login page URL
login_url is how membership and white-label sites hide wp-login.php. Return a full URL, not a path fragment.
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apply_filters( 'login_url', string $login_url, string $redirect, bool $force_reauth );Example
add_filter( 'login_url', function( $url ) {
return home_url( '/my-login/' );
} );Common Use Cases
the_excerptFilters the displayed post excerpt
the_excerpt filters the final excerpt string, whether it was typed manually or auto-generated — use excerpt_length/excerpt_more to shape the auto version instead.
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apply_filters( 'the_excerpt', string $post_excerpt );Example
add_filter( 'the_excerpt', function( $excerpt ) {
return '<div class="excerpt-wrap">' . $excerpt . '</div>';
} );Common Use Cases
excerpt_moreFilters the '[…]' string appended to auto-generated excerpts
excerpt_more only changes the trailing string on auto-generated excerpts — it does nothing to a manually written excerpt.
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apply_filters( 'excerpt_more', string $more_string );Example
add_filter( 'excerpt_more', function() {
return ' <a href="' . get_permalink() . '">Read more →</a>';
} );Common Use Cases
post_classFilters the CSS classes on a single post's wrapper element
post_class runs once per post inside the loop — unlike body_class, which runs once per page — so keep the callback fast if you're looping many posts.
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apply_filters( 'post_class', string[] $classes, string[] $css_class, int $post_id );Example
add_filter( 'post_class', function( $classes, $css_class, $post_id ) {
if ( has_post_thumbnail( $post_id ) ) {
$classes[] = 'has-thumbnail';
}
return $classes;
}, 10, 3 );Common Use Cases
document_title_partsFilters the parts that build the <title> tag on modern themes
document_title_parts is the modern replacement for wp_title — it works with an array of parts, not a raw string, so you edit pieces instead of parsing text.
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apply_filters( 'document_title_parts', array $title );Example
add_filter( 'document_title_parts', function( $title ) {
if ( is_singular( 'book' ) ) {
$title['title'] .= ' | Book Review';
}
return $title;
} );Common Use Cases
wp_nav_menu_itemsFilters the HTML list items of a rendered nav menu
wp_nav_menu_items lets you append or alter menu markup without editing the menu in the admin — useful for injecting a login/cart link at the end.
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apply_filters( 'wp_nav_menu_items', string $items, stdClass $args );Example
add_filter( 'wp_nav_menu_items', function( $items, $args ) {
if ( 'primary' !== $args->theme_location ) {
return $items;
}
$items .= is_user_logged_in()
? '<li><a href="' . wp_logout_url() . '">Log out</a></li>'
: '<li><a href="' . wp_login_url() . '">Log in</a></li>';
return $items;
}, 10, 2 );Common Use Cases
wp_mail_fromFilters the from-address used by wp_mail()
wp_mail_from fixes the wordpress@yourdomain.com sender WordPress uses by default — pair it with wp_mail_from_name to fully brand outgoing mail.
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apply_filters( 'wp_mail_from', string $from_email );Example
add_filter( 'wp_mail_from', function() {
return 'no-reply@example.com';
} );
add_filter( 'wp_mail_from_name', function() {
return get_bloginfo( 'name' );
} );Common Use Cases
upload_mimesFilters the list of file types allowed for upload
upload_mimes controls what get_allowed_mime_types() and the uploader accept — adding a type here does not make it safe by itself; WordPress still runs its own file-content checks.
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apply_filters( 'upload_mimes', array $mime_types, WP_User|int|null $user );Example
add_filter( 'upload_mimes', function( $mimes ) {
$mimes['svg'] = 'image/svg+xml';
return $mimes;
} );Common Use Cases
comment_textFilters the displayed text of a single comment
comment_text is where you'd add nofollow to links, auto-linkify text, or moderate content on display — it doesn't change what's stored in the database.
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apply_filters( 'comment_text', string $comment_text, WP_Comment|null $comment, array $args );Example
add_filter( 'comment_text', function( $comment_text, $comment ) {
if ( $comment && ! $comment->user_id ) {
$comment_text .= '<span class="guest-badge">Guest</span>';
}
return $comment_text;
}, 10, 2 );Common Use Cases
template_includeFilters the final template file path WordPress is about to load
template_include is the very last stop in the template hierarchy — return an absolute path to a PHP file and WordPress loads exactly that, bypassing the rest of the hierarchy.
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apply_filters( 'template_include', string $template );Example
add_filter( 'template_include', function( $template ) {
if ( is_singular( 'book' ) ) {
$custom = plugin_dir_path( __FILE__ ) . 'templates/single-book.php';
if ( file_exists( $custom ) ) {
return $custom;
}
}
return $template;
} );Common Use Cases
admin_footer_textFilters the text shown in the bottom-left of every admin page
admin_footer_text is a lightweight branding hook — agencies commonly use it to replace WordPress's default footer credit with their own support link.
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apply_filters( 'admin_footer_text', string $text );Example
add_filter( 'admin_footer_text', function() {
return 'Managed by Acme Agency — <a href="https://example.com/support">Get support</a>';
} );Common Use Cases
script_loader_tagFilters the final <script> tag markup for an enqueued script
script_loader_tag is how you add async/defer or a nonce to a specific enqueued script without touching the theme's enqueue logic wholesale.
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apply_filters( 'script_loader_tag', string $tag, string $handle, string $src );Example
add_filter( 'script_loader_tag', function( $tag, $handle ) {
if ( 'my-script' !== $handle ) {
return $tag;
}
return str_replace( ' src', ' defer src', $tag );
}, 10, 2 );Common Use Cases
render_blockFilters the final HTML output of every rendered block
render_block runs for every block on the page, core and custom alike — check $block['blockName'] or it will touch content you didn't intend to change.
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apply_filters( 'render_block', string $block_content, array $block );Example
add_filter( 'render_block', function( $block_content, $block ) {
if ( 'core/image' !== $block['blockName'] ) {
return $block_content;
}
return str_replace( '<img', '<img loading="lazy"', $block_content );
}, 10, 2 );Common Use Cases
rest_prepare_postFilters the REST API response for a single post before it's sent
rest_prepare_post lets you add or remove fields on the /wp/v2/posts response without touching register_rest_field — useful for last-mile shaping of what the API returns.
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apply_filters( 'rest_prepare_post', WP_REST_Response $response, WP_Post $post, WP_REST_Request $request );Example
add_filter( 'rest_prepare_post', function( $response, $post ) {
$response->data['reading_time'] = ceil( str_word_count( $post->post_content ) / 200 );
return $response;
}, 10, 2 );Common Use Cases
wp_get_attachment_image_attributesFilters the HTML attributes of an image rendered by wp_get_attachment_image()
wp_get_attachment_image_attributes touches every image WordPress renders through its own media functions — including inside blocks and thumbnails — so scope changes carefully.
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apply_filters( 'wp_get_attachment_image_attributes', array $attr, WP_Post $attachment, string|array $size );Example
add_filter( 'wp_get_attachment_image_attributes', function( $attr ) {
$attr['loading'] = 'lazy';
$attr['decoding'] = 'async';
return $attr;
} );Common Use Cases
cron_schedulesRegisters custom cron interval schedules
cron_schedules is the only way to add a custom recurring interval — WordPress ships with hourly, twicedaily, and daily only.
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apply_filters( 'cron_schedules', array $schedules );Example
add_filter( 'cron_schedules', function( $schedules ) {
$schedules['every_fifteen_minutes'] = [
'interval' => 15 * MINUTE_IN_SECONDS,
'display' => 'Every 15 Minutes',
];
return $schedules;
} );Common Use Cases
authenticateThe core WordPress login/authentication filter
authenticate is the chain that decides whether login credentials are valid — every auth method, from core's own password check to SSO plugins, hooks into this same filter.
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apply_filters( 'authenticate', WP_User|WP_Error|null $user, string $username, string $password );Example
add_filter( 'authenticate', function( $user, $username ) {
if ( 'blocked_user' === $username ) {
return new WP_Error( 'blocked', 'This account is disabled.' );
}
return $user;
}, 30, 3 );Common Use Cases
rest_pre_dispatchShort-circuits a REST API request before routing
rest_pre_dispatch lets you intercept a REST API request before WordPress even matches it to a route — the earliest point to block or fake a response.
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apply_filters( 'rest_pre_dispatch', mixed $result, WP_REST_Server $server, WP_REST_Request $request );Example
add_filter( 'rest_pre_dispatch', function( $result, $server, $request ) {
if ( str_starts_with( $request->get_route(), '/my-plugin/v1' ) && ! is_user_logged_in() ) {
return new WP_Error( 'forbidden', 'Login required', [ 'status' => 401 ] );
}
return $result;
}, 10, 3 );Common Use Cases
manage_posts_columnsAdds or removes columns on the admin post list table
manage_posts_columns controls what shows up in wp-admin's post list table — add a custom column here, then fill it with manage_posts_custom_column.
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apply_filters( 'manage_posts_columns', string[] $columns );Example
add_filter( 'manage_posts_columns', function( $columns ) {
$columns['word_count'] = 'Word Count';
return $columns;
} );Common Use Cases