How does WordPress handle permalinks?

Question

WordPress auto corrects the permalinks(URLs) even if it is entered incorrectly. For e.g. WordPress will land you in example.com/some-post even if you enter example.com/idontexist/some-post or even example.com/some

It could be that, WordPress uses RegEx like or some matching algorithm that compares from right to left and if it finds a match, it will take you to the page even if there are /.*/ left on the left. Just a guess! How does WordPress do this?

Edit: I also noticed that the .htaccess file checks for virtual file/directories using !f and !d and redirects the request to index.php on the blog folder.

Answer 1

The redirect_canonical function in /wp-includes/canonical.php is called on any given URL and will attempt to best-guess the URL the user wanted, and redirect them to there, when a URL does not exist. It has a whole huge amount of code to do this for all sorts of common errors.

Answer 2

Use @JanFabry "Rewrite Analyzer" Plugin, over here in the "official" WPSE Plugin repository

Answer 3

It's pretty simple. WordPress makes use of LIKE operator in SQL query to guess the complete URL from the partial URL when it's a 404 page

Check this code taken from /wp-includes/canonical.php redirect_guess_404_permalink() function

$where = $wpdb->prepare( 'post_name LIKE %s', $wpdb->esc_like( get_query_var( 'name' ) ) . '%' );