WooCommerce checkout 500 error — diagnose and fix it
Quick answer
A WooCommerce checkout 500 error is a server-side crash, usually from a plugin or theme conflict after an update, a PHP memory limit hit, or a fatal error in custom code on the checkout hook. The fastest path is to read the server error log for the exact fatal line, disable the offending plugin or revert the change, and confirm with a real test order — on managed hosting Liulum can roll the change back automatically.
Symptoms
- Customers hit a blank page or "HTTP 500" at the payment step
- Orders stop while the rest of the site still loads
- The error appears right after a plugin, theme, or PHP update
- The site works for admins but fails for customers at checkout
Common causes
- A plugin or theme conflict introduced by a recent update
- PHP memory limit exhausted during checkout processing
- A fatal error in custom code hooked into the checkout flow
- A corrupted file or failed update leaving the site half-migrated
How to check
- 1.Read the server/PHP error log for the fatal error and file path
- 2.Enable WooCommerce logging and reproduce the checkout once
- 3.Deactivate plugins one by one (or bulk, then reactivate) to isolate the conflict
- 4.Switch to a default theme temporarily to rule the theme in or out
How to fix it
1. Read the fatal line
The PHP/server error log names the exact file and function that crashed — this is the single fastest way to identify the culprit plugin or code.
2. Disable or revert
Deactivate the offending plugin or revert the update/custom code, then place a real test order to confirm checkout works again.
3. Raise memory if needed
If the log shows a memory-exhausted error, increase the PHP memory limit and retest.
4. Roll back safely
On sites Liulum manages, an allow-listed rollback can restore the last healthy version automatically and verify checkout — reversible and logged — so downtime is seconds, not hours.
How Liulum helps
Liulum watches this path continuously, tells you in plain English the moment it breaks, and on sites it manages can run a safe, allow-listed, reversible repair automatically — so an outage lasts seconds, not hours.
Protect your storeFrequently asked questions
What causes a 500 error only at WooCommerce checkout?
The checkout runs extra code (payment gateways, tax, shipping, order hooks) that other pages don't, so a plugin conflict or fatal error there crashes checkout while the rest of the site loads. The error log names the exact cause.
How do I fix it without taking the whole site down?
Reproduce once with logging on, read the fatal line, then disable just the offending plugin or revert the specific change rather than disabling everything. Confirm with a real test order.
Can Liulum auto-repair a WooCommerce 500?
On managed WooCommerce sites, yes — Liulum can run a safe, allow-listed rollback to the last healthy state and verify the checkout automatically, every action logged and reversible. It also alerts you with the plain-English cause.