DevTips – How to Stop WordPress From Guessing URLs

The other day I was working on one of my projects and I encountered an unexpected behavior: if you write the URL of a page in a WordPress site incorrectly, WordPress will try to guess what page you were trying to access and “fix” your request so that you get the proper page and not a 404 error.

Let’s look at an example, which is easier to understand.

A few weeks ago I wrote a blog post called Discover where you added errors in the code using Git Bisect. If you click on the link, you will see that its URL is https://neliosoftware.com/blog/git-bisect-to-find-faulty-commit/. Well, what would happen if you typed in a URL that’s close to this one, but still incorrect? Let’s try it: type https://neliosoftware.com/blog/git-bisect in your browser and you’ll see that WordPress performs a 301 redirection and makes sure you see my post:

The thing is, this trick doesn’t always work. Instead of writing “git-bisect” (which is how the post’s slug begins), try something like “faulty-commit” (which is also part of the slug) and you’ll finally get the 404 error:

So… yup, theses guesses work on very specific scenarios.

Is it good or bad that WordPress tries to fix a URL that does not exist instead of returning a 404? According to bug #16557 reported 9 years ago, there should be a filter to deactivate this behavior if the user wishes so. But although we have a patch for it, for some reason it never made it into core so… what if you wanted to deactivate this behavior?

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How to Avoid URL Auto-Correction

To solve this “problem” (assuming you think it is a problem), you have two options. Either you apply the solution proposed by Andrew Nacin (one of the leading WordPress developers) by adding this small function:

function remove_redirect_guess_404_permalink( $redirect_url ) {
  if ( is_404() ) {
    return false;
  }//end if
  return $redirect_url;
}//end remove_redirect_guess_404_permalink()
add_filter( 'redirect_canonical', 'remove_redirect_guess_404_permalink' );

in your WordPress (following the instructions we shared with you a few months ago) or, even simpler, you install the Disable URL Autocorrect Guessing plugin by Hauke Pribnow.

Featured image by David Brooke Martin on Unsplash.