If you’re updating WordPress, replace its old core files with the official files for the new release; don’t delete the whole installation or remove an unexplained file just because it looks old. Back up and verify the database and site files first, preserve wp-config.php and wp-content, and identify any specific leftover by its full path and WordPress version before considering removal.
First, decide what “old WordPress core files” means
There are two different tasks that are easy to confuse:
- Updating WordPress: replace the old core directories and files with those from the intended official release. This is a core update, not a command to wipe the WordPress directory.
- Removing one leftover: investigate a particular file that remains after an update. A file is not safe to delete just because it appears old or was not included in the new release.
For a routine update, use the WordPress dashboard updater if it is available, or follow WordPress’s manual update instructions. If you have a specific leftover, establish what it is before deleting anything.
What to keep when replacing core files
wp-config.php, which contains site configuration.- The existing
wp-contentdirectory, which contains site content such as plugins, themes, and uploads. WordPress explicitly says: “Do NOT delete your existingwp-contentfolder.” - Site-specific files and settings, including custom
.htaccessrules and a site-created rootrobots.txt, where applicable.
WordPress’s shorter update guide describes replacing wp-admin and wp-includes, uploading the new root-level core files, and preserving the existing wp-content directory. The Advanced Administration Handbook’s manual upgrade guidance also identifies files and folders to retain. Follow the instructions that match your installation and release; broad wording about deleting old files is not permission to delete every item in the site directory.
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Safely replace core files during a manual update
- Back up the database and all WordPress files. Include files such as
.htaccess. Verify that the backups exist and can be restored before proceeding. WordPress’s manual upgrade guidance recommends backing up both. - Deactivate plugins as directed in WordPress’s manual upgrade procedure. Download and extract the official WordPress package for the release you intend to install.
- Replace the core directories and files. Remove the old
wp-adminandwp-includesdirectories, then upload their new versions. Overwrite applicable root-level core files with the package’s files. Where package files insidewp-contentapply, upload those into the existingwp-contentdirectory; do not replace or delete that directory. - Preserve configuration and site-specific files. Do not delete
wp-config.php. Keep custom.htaccessrules and a site-created rootrobots.txtwhere relevant, and apply the official procedure’s specific exceptions rather than a blanket deletion. - Run the upgrade program if prompted, then check the site. Review the site, permalinks, themes, plugins, and any changes relevant to the update.
For a routine update, the built-in WordPress updater is generally the simpler route: WordPress handles replacement and its defined cleanup. Manual replacement is for situations where you are following the manual procedure and have file access, verified backups, and a clear understanding of which files must remain.
What to do if an old file remains after updating
WordPress’s automatic updater processes a defined list of old files. Its upgrade FAQ says files outside that list and absent from the release distribution remain in place. The update_core() reference describes copying new files, upgrading the database, and then removing old files; it also documents interrupted cleanup as a possible failure case.
That means a leftover may be an orphan, a site-specific file, or evidence of an incomplete update. The updater’s behavior does not establish that an arbitrary file is safe to remove. Before deleting a named file:
- Record its full path, including its directory.
- Identify the installed WordPress version and determine whether the update completed successfully.
- Compare the file with the official files for that specific release and determine whether it belongs to your site or another component.
- Keep a verified backup before removing it. If you cannot establish that the file is obsolete, leave it in place and get version-specific help.
Use WP-CLI if you already administer the site from the command line
WP-CLI documents wp core update and wp core verify-checksums. The first is a command-line route for updating WordPress core; the second checks core files against WordPress.org checksums. Check the installed WP-CLI command documentation for the options and requirements that apply to your setup.
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Before running either command on a live site, confirm that you are in the correct WordPress installation and that you have appropriate access, a verified backup, and a clear update state. Checksum verification can help assess core files, but it does not by itself prove that a separate, unexplained file is safe to delete.
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