For the most part WordPress does a decent job of renaming and cleaning up attachment media filenames, but sometimes it’s just not quite good enough. When it comes to UTF8 characters or accents it tends to just ignore them as they’re (mostly) considered web safe.

This can become an issue when third party services crawl your site and struggle with the encoding e.g. Facebook’s Sharing Debugger which is where I had trouble. Of course it’s also not great for SEO. In an Ideal world you want the featured image filename to closely mirror the post title, not be “Screenshot 2016-08-05T22:03:22.jpg”.

Cleaner Filenames

If all you want to do is clean up your filenames and remove UTF8 characters and accents then just place this code in your functions.php (will only clean up all new filenames). This code was originally posted by Vaughn Royko.

Update: I’ve also released it as a super simple plugin for those that prefer it. Check it out on WordPress.org here.

/**
 * Produces cleaner filenames for uploads
 *
 * @param  string $filename
 * @return string
 */
function wpartisan_sanitize_file_name( $filename ) {

	$sanitized_filename = remove_accents( $filename ); // Convert to ASCII

	// Standard replacements
	$invalid = array(
		' '   => '-',
		'%20' => '-',
		'_'   => '-',
	);
	$sanitized_filename = str_replace( array_keys( $invalid ), array_values( $invalid ), $sanitized_filename );

	$sanitized_filename = preg_replace('/[^A-Za-z0-9-\. ]/', '', $sanitized_filename); // Remove all non-alphanumeric except .
	$sanitized_filename = preg_replace('/\.(?=.*\.)/', '', $sanitized_filename); // Remove all but last .
	$sanitized_filename = preg_replace('/-+/', '-', $sanitized_filename); // Replace any more than one - in a row
	$sanitized_filename = str_replace('-.', '.', $sanitized_filename); // Remove last - if at the end
	$sanitized_filename = strtolower( $sanitized_filename ); // Lowercase

	return $sanitized_filename;
}

add_filter( 'sanitize_file_name', 'wpartisan_sanitize_file_name', 10, 1 );

So what does it do:

File: ~My WordPress Upload~.jpg
Default WordPress: My-WordPress-Upload.jpg
Custom Solution: my-wordpress-upload.jpg

File: ÐÕçument full of $$$.pdf
Default WordPress: ÐÕçument-full-of-.pdf
Custom Solution: document-full-of.pdf

File: Really%20Ugly%20Filename-_-That_-_Is_Too Common…..png
Default WordPress: Really-Ugly-Filename-_-That_-_Is_Too-Common…..png
Custom Solution: really-ugly-filename-that-is-too-common.png

Complete SEO Solution

If you want a more complete solution we’re currently develop a plugin to do just that. It’ll be able to:

– Sanitize and clean all new media upload filenames
– Optionally sanitize and clean all existing media filenames
– Allow manual renaming of all existing media
– Auto renaming of filenames based on post title, even when the post is updated