While updating, WordPress takes the site offline for a moment and shows the text Briefly unavailable for scheduled maintenance. Check back in a minute. Normally that lasts a few seconds. If it does not clear, the update was interrupted and the site stayed locked.
If the update is still running, interrupting it does more harm than waiting. Reload the page after a minute. Only if the text is still there, move on to the next step.
Connect over FTP or SFTP to the site root, the directory that holds wp-config.php and wp-content. You will find a file called .maintenance. It starts with a dot, so many clients hide it and you need to turn on showing hidden files. Delete it and reload the site. It opens right away. Making the connection is covered in our guide to FTP and SFTP.
The site is open but the work is unfinished. Log in and look at the updates screen to see whether a plugin or a theme is still on the old version. Run the update again, one at a time. If the same update keeps stopping at the same point, that is not chance, it means it does not fit inside the server time or memory limit.
If the maintenance text is still visible after the file is gone, it is coming from a cache rather than from WordPress. Clear the site cache and the browser cache, and try in a private browser window.
Then the interrupted update managed to break something else. The usual outcome is a blank page or a critical error, and both have a guide of their own. See the white screen in WordPress and a critical error on the site.
Do not start several updates at once on a slow connection and do not close the browser mid update. That is exactly how maintenance mode gets stuck. Take a backup before large updates, see our guide on backing up a site.
We release the lock, finish the interrupted update and check that it did not break anything else. We also find out why it stopped, because otherwise the same thing happens next time.
