Disable page title rewrite feature in WordPress SEO plugin

disable-title-rewrite-wordpress-seo.php

<?php

// Remove the wp_title filter
add_action( 'init', 'remove_wpseo_title_rewrite' );

function maybe_remove_wpseo_title_rewrite() {
        global $wpseo_front;

	remove_filter( 'wp_title', array( $wpseo_front, 'title' ), 15 );
}

// Remove the title metabox from backend UI
add_filter( 'init', 'remove_wpseo_title_rewrite_metabox' );

function remove_wpseo_title_rewrite_metabox( $metaboxes ) {
	if ( isset( $metaboxes['title'] ) )
		unset( $metaboxes['title'] )
	
	return $metaboxes;
}

In the latest Yoast SEO version, you'll need to use the following to remove the wp_title filter:

// Remove the wp_title filter
 add_action( 'init', 'remove_wpseo_title_rewrite' );
 function remove_wpseo_title_rewrite () {
    $wpseo_front = WPSEO_Frontend::get_instance();

    remove_filter( 'pre_get_document_title', array( $wpseo_front, 'title' ), 15 );
    remove_filter( 'wp_title', array( $wpseo_front, 'title' ), 15 );
}

An improvement of iamazik code, which avoids a PHP error when YOAST plugin is disabled:

// Remove the wp_title filter
if ( class_exists('WPSEO_Frontend') ) {
	 add_action( 'init', 'remove_wpseo_title_rewrite' );
	 function remove_wpseo_title_rewrite () {
		$wpseo_front = WPSEO_Frontend::get_instance();

		remove_filter( 'pre_get_document_title', array( $wpseo_front, 'title' ), 15 );
		remove_filter( 'wp_title', array( $wpseo_front, 'title' ), 15 );
	}
}