WooCommerce 9 marks a significant upgrade. New checkout experience, High-Performance Order Storage (HPOS) as default, and a more modern architecture under the hood. It affects everyone running WooCommerce.
Block-based checkout
The new checkout builds on Gutenberg blocks instead of the old shortcode-based one. Faster, mobile-friendly, and easier to customize. The old checkout page still works but is no longer the default. Switch if you haven't already.
HPOS (High-Performance Order Storage)
Orders are stored in a dedicated table instead of wp_posts and wp_postmeta. The result: faster order management, better search, scalability. Stores with thousands of orders notice the difference immediately. Enable under WooCommerce → Settings → Advanced → Features.
Check that all your plugins are HPOS-compatible before enabling. Most major plugins (Subscriptions, Bookings, Stripe) already are. Run in "sync mode" (both tables) during a transition period.
Product blocks
New blocks: Product Collection, Featured Category, Cart Cross-Sells. They replace the old WooCommerce widgets with modern blocks that work with Full Site Editing. More flexibility for how products are displayed.
Performance
Less JavaScript, faster AJAX calls, better caching compatibility. WooCommerce 9 is measurably faster than 8.x, especially on category pages and at checkout.
Upgrade strategy
Test in staging. Check HPOS compatibility. Switch to the block checkout page if you're still using the shortcode version. Take a backup. It's a major version, but the benefits are clear.