WooCommerce Checkout Not Working: Root-Cause Fixes
I diagnose and fix broken WooCommerce checkouts—resolving infinite spinning loaders, broken 'Place Order' buttons, and silent AJAX crashes within hours.
The Technical Challenge
A broken checkout directly halts business cash flow. When customers click 'Place Order' and the screen hangs or returns an unhelpful error message, customers abandon their purchases. The underlying issue is almost always a fatal PHP error inside a checkout hook, malformed JSON returned from `?wc-ajax=checkout`, or a JavaScript exception breaking DOM submission.
Common Technical Symptoms & Breakdowns:
- ✕ Infinite spinning wheel after clicking the 'Place Order' button
- ✕ Browser DevTools shows a red 500 or 400 error on `/?wc-ajax=checkout`
- ✕ Console error: `Uncaught SyntaxError: Unexpected token < in JSON at position 0`
- ✕ Cart empties unexpectedly before payment details can be entered
- ✕ Shipping methods fail to calculate or display 'No shipping options available'
My Diagnostic & Engineering Methodology
I follow a deterministic diagnostic process: 1) inspect server PHP error logs to catch fatal errors during the checkout POST payload, 2) inspect Network panel responses to isolate PHP warnings or notices corrupting the JSON response string, 3) verify that `wc-checkout.js` is not suppressed or conflicting with minification plugins, and 4) test payment gateway REST handlers for valid nonces and customer session cookies.
All testing occurs in an isolated staging clone or container before touching production files or active databases.
Inspecting error logs, network payloads, and execution call stacks to isolate the exact failing hook or query.
Implementing standards-compliant code with PSR-4 namespaces, proper sanitization, and zero core overrides.
End-to-end device testing, performance benchmarking, Git commits, and full architectural documentation.
Technologies, APIs & Architectural Standards:
What I Deliver
Rapid isolation and resolution of the exact script or server error causing the checkout crash
Removal of theme or plugin collisions without losing required store functionality
Comprehensive mobile and desktop transaction test to ensure full checkout flow stability
Permanent fix implementation preventing recurrence during future plugin updates
Prerequisites
To ensure rapid kickoff and zero delays, the following items are required before we begin:
- ✓ Staging environment access or maintenance-window server credentials
- ✓ Server error logs (`error_log` or hosting log dashboard)
- ✓ Active payment gateway sandbox mode or live test instructions
Frequently Asked Questions
Q. What causes the 'Unexpected token < in JSON' error in WooCommerce checkout?
This happens when a PHP error, notice, or blank HTML space is printed by a theme or plugin before WooCommerce sends its JSON response. The browser expects pure JSON, but receives HTML (starting with '<'), causing the JavaScript parser to crash and the checkout spinner to freeze indefinitely.
Q. How quickly can you fix a live broken checkout?
I treat checkout failures as emergency incidents. I start forensic triage immediately upon receiving server credentials and resolve the majority of issues within 4 to 12 hours.
Q. Will fixing this require changing my theme or plugins?
Usually not. In 95% of cases, the issue is caused by a specific conflicting hook or script that can be cleanly dequeued, patched, or isolated in code without requiring a full theme redesign.
Related Engineering Services
All Services →WooCommerce Checkout Troubleshooting & Root-Cause Fixes
Forensic diagnosis and code-level fixes for broken WooCommerce checkout: spinning wheel errors, AJAX 500 failures, payment drops, and session loss.
WooCommerce Payment Failing: Troubleshooting & Fixes
Fix WooCommerce payment failures: order status stuck on pending, payment webhook drops, 3D Secure verification crashes, and currency mismatches.
WooCommerce Engineering & Scalable Store Architecture
Scalable WooCommerce engineering for high-volume stores. High-Performance Order Storage (HPOS), custom checkout flows, and decoupled commerce architectures.
Slow WooCommerce Store: Forensic Speed & Database Fixes
Fix slow WooCommerce stores: HPOS migration, autoloaded options cleanup, slow database query indexing, and instant checkout acceleration.
Is your WooCommerce checkout costing you sales right now?
Get direct engineering triage to restore your checkout immediately.