Migrate WooCommerce Legacy REST API Before 9.0
WooCommerce 9.0 (June 11, 2024) removes Legacy REST API; detect usage via admin notices/logs since 8.5, install free plugin for transition, contact vendors to switch to v3 API.
Detect Legacy REST API Usage to Avoid Disruptions
Check WooCommerce → Settings → Advanced → Legacy REST API: if disabled, you're safe. Since WooCommerce 8.5, active usage triggers admin notices with logs showing routes like /customers/count and plugins like shipshapeshipping/1.2.3—use this to identify and contact vendors. Also scan WooCommerce → Settings → Advanced → Webhooks for 'legacy' webhooks, and REST API keys screen: empty lists signal no dependency. No keys doesn't guarantee safety, but logs do; monitor for weeks with plugin active to confirm zero usage before removal.
Install Transition Plugin for Seamless Woo 9.0 Upgrade
Download WooCommerce Legacy REST API plugin from wordpress.org/plugins/woocommerce-legacy-rest-api. WooCommerce 8.8+ auto-installs it if usage detected (block via docs if unwanted). It restores old endpoints temporarily, buying time for migrations. Post-9.0, re-install WooCommerce core if class errors like WC_Legacy_API not found occur during plugin activation—upload fresh ZIP via Plugins → Add New → Upload. Safe to remove after confirming no logs for weeks/months.
Handle Compatibility and Force Vendor Migration
Legacy API conflicts with High-Performance Order Storage (HPOS): enable Compatibility Mode at WooCommerce → Settings → Advanced → Features if both needed. Push third-parties (e.g., shipping services on v1 endpoints) to WooCommerce REST API v3 (docs: woocommerce.github.io/woocommerce-rest-api-docs). Keys work across versions with plugin; no new keys required. Common pitfalls from users: site crashes post-auto-install (disable if no logs), legacy webhooks breaking connections—install plugin first, then migrate. Prioritize: detect → plugin → monitor → contact vendors → remove.