If you want to exclude wordpress pages from the search then you have to add following code in your themes function.php file.

function SearchFilter($query) {
if ($query->is_search) {
$query->set('post_type', 'post');
}
return $query;
}
add_filter('pre_get_posts','SearchFilter');

Above code filters all the posts retrieved by the wordpress query and set post_type equal to “post”.

Source

WordPress Filters
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