WP-Cron
WP-Cron is WordPress's scheduler. It publishes scheduled posts, checks for updates and runs plugins' timed jobs. It has no clock of its own. Page loads start it, so on a quiet site, or one that cannot reach itself, tasks run late or not at all.
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- WP Ministry
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In short
- WP-Cron runs when a page is loaded, not at a set time. A task that falls due waits for the next visit.
- DISABLE_WP_CRON in wp-config.php stops page loads from starting it. That is right only when a cron job on the server requests wp-cron.php instead.
- `wp cron event list` shows every task and when it runs next. `wp cron event run --due-now` runs what is waiting.
WP-Cron is the part of WordPress that runs tasks at a set time. WordPress uses it to publish scheduled posts and to check for updates. Plugins use it for timed jobs of their own, such as a backup. The name comes from cron, the scheduler on Unix servers, but WP-Cron has no clock.
A task runs only after someone loads a page. WordPress's handbook says WP-Cron "is only triggered on page load". On each load WordPress checks its list of tasks. If one is due, it sends a request to its own wp-cron.php file, which runs it. The handbook's example: a task set for 2:00 PM on a site nobody visits until 5:00 PM runs at 5:00 PM. It is late, not lost.
The handbook and the code differ on one detail. The handbook says a due task is called during that page load. The current source, wp-includes/cron.php, makes the check at the end of the request (since WordPress 6.9) and runs the task in a separate request to wp-cron.php, at most once every 60 seconds, so a visitor does not wait for it. The source is what your site runs.
Where you meet it
wp-cron.php, in the folder WordPress is installed in. In the server's access log its requests readwp-cron.php?doing_wp_cron=followed by a number.define( 'DISABLE_WP_CRON', true );inwp-config.php. The line stops page loads from starting WP-Cron. The handbook gives it as the last step, after the server's own scheduler has been set to requestwp-cron.php.- Tools, then Site Health. A healthy site lists "Scheduled events are running" among its passed tests. A site in trouble shows "A scheduled event is late" or "A scheduled event has failed".
- The Posts screen. A scheduled post whose time has passed shows "Missed schedule".
What goes wrong
- A quiet site runs late. With no page loads, nothing starts the tasks. A scheduled post stays unpublished: see how to fix "Missed schedule". A plugin's nightly backup waits for the next visitor. How to schedule automatic backups shows how to put WP-Cron on a real clock.
- It was switched off and nothing took its place. With
DISABLE_WP_CRONset and no cron job on the server, no scheduled task is started at all. Set up the cron job first, then add the line. - The site cannot reach itself. WP-Cron depends on the site sending a request to its own address. Site Health calls this a loopback request and says such requests "are used to run scheduled events". If the server or a security rule refuses it, tasks stop while the site looks fine.
- A heavy task slows the dashboard. The task runs as a request on the same server as your pages. The guide to a slow WordPress admin shows how to find one.
- WooCommerce's background jobs stall with it. Action Scheduler, the queue WooCommerce uses, is started by WP-Cron once a minute. Without it, the queue moves only while someone is working in the dashboard.
How to look at yours
With WP-CLI, this lists every task, when it runs next and how often it repeats:
wp cron event listA new site lists wp_version_check, wp_update_plugins and wp_update_themes, each repeating every 12 hours. To run everything that is due now:
wp cron event run --due-nowCommon questions
Is WP-Cron the same as a cron job?
No. A cron job is run by the server's own scheduler at a set time, whether or not anyone visits. WP-Cron is part of WordPress and runs only after a page is loaded. The two are often combined: a cron job requests wp-cron.php at an interval you choose, and DISABLE_WP_CRON stops page loads from doing the same work.
Should I disable WP-Cron?
Only once something else requests wp-cron.php on a schedule. With the line in place and no cron job, scheduled posts, update checks and plugin schedules all stop.