WordPress at a glance
action is not described

init action-hook . WP 1.5.0

Fires after WordPress has finished loading but before any headers are sent.

Most of WP is loaded at this stage, and the user is authenticated. WP continues to load on the 'init' hook that follows (e.g. widgets), and many plugins instantiate themselves on it for all sorts of reasons (e.g. they need a user, a taxonomy, etc.).

If you wish to plug an action once WP is loaded, use the 'wp_loaded' hook below.

Usage

add_action( 'init', 'action_function_name_3277' );
function action_function_name_3277(){
	// action...
}

Where the hook is called

In file: /wp-settings.php
init
wp-settings.php 505
do_action( 'init' );

Where the hook is used (in WP core)

wp-includes/blocks/archives.php 147
add_action( 'init', 'register_block_core_archives' );
wp-includes/blocks/categories.php 102
add_action( 'init', 'register_block_core_categories' );
wp-includes/blocks/latest-posts.php 132
add_action( 'init', 'register_block_core_latest_posts' );
wp-includes/blocks/shortcode.php 32
add_action( 'init', 'register_block_core_shortcode' );
wp-includes/class-wp-customize-manager.php 371
remove_action( 'init', 'wp_cron' );
wp-includes/class.wp-scripts.php 132
add_action( 'init', array( $this, 'init' ), 0 );
wp-includes/default-filters.php 447
add_action( 'init', 'rest_api_init' );
wp-includes/default-filters.php 529
add_action( 'init', 'wp_widgets_init', 1 );
wp-includes/default-filters.php 511
add_action( 'init', 'create_initial_taxonomies', 0 ); // highest priority
wp-includes/default-filters.php 489
add_action( 'init', 'kses_init' );
wp-includes/default-filters.php 475
add_action( 'init', 'create_initial_post_types', 0 ); // highest priority
wp-includes/default-filters.php 369
add_action( 'init', 'wp_schedule_delete_old_privacy_export_files' );
wp-includes/default-filters.php 399
add_action( 'init', '_show_post_preview' );
wp-includes/default-filters.php 349
add_action( 'init', 'smilies_init', 5 );
wp-includes/default-filters.php 332
add_action( 'init', 'wp_cron' );
wp-includes/default-filters.php 303
add_action( 'init', 'check_theme_switched', 99 );
wp-includes/default-filters.php 131
add_action( 'init', 'wp_init_targeted_link_rel_filters' );
wp-includes/ms-default-filters.php 16
add_action( 'init', 'ms_subdomain_constants' );
wp-includes/ms-default-filters.php 25
add_action( 'init', 'maybe_add_existing_user_to_blog' );
wp-includes/update.php 824
add_action( 'init', 'wp_schedule_update_checks' );