The short answer: in a shop, or on any site with accounts, the same page is not the same for everyone: the cart, the total, the name at the top, sometimes the price in a currency. A CDN can only store what is the same for everyone. If it stores a personal page, it hands it to the next visitor: swapped carts, someone seeing another person’s account, or payments that never get confirmed. The rule is simple: static files, always; public pages, only with careful rules; anything with a session, never. We do not sell a CDN: what follows applies to whichever CDN you choose, on an account of your own, opened directly with that provider.
What always stays out of the CDN cache
| What |
Why |
| Cart, checkout, order confirmation page |
Different for every customer. Cached, they show someone else’s cart or order. |
| Customer account, members area, admin dashboard (on WordPress, /wp-admin/ and wp-login.php) |
They hold personal data and sessions. |
| Requests carrying a session or cart cookie |
On WordPress, wordpress_logged_in_; on WooCommerce, woocommerce_items_in_cart, woocommerce_cart_hash and wp_woocommerce_session_. When a request carries one of these, the CDN should pass it straight to the origin. |
| Requests that change something: form posts (POST), ?add-to-cart=, AJAX calls (admin-ajax.php, ?wc-ajax=) |
They are actions, not reads. A cached action returns the old answer and does nothing. |
| Payment return addresses and webhooks |
They must always reach the origin: no cache, no challenge or captcha, no country blocking. Otherwise the customer pays and the order stays pending. |
| Search, filters, prices by currency or country |
They change with the visitor. Either do not cache them, or make sure the cache key includes whatever changes. |
| Pages with forms (contact, comments, login) |
They carry security codes that expire. An old copy gives “the link has expired” or a rejected form. Short lifetime, or out of the cache. |
Setting up the rules without breaking the shop
| 1 |
Start with static files only (images, CSS, JS, fonts). It is what many CDNs do by default, and in a shop with lots of photographs it is where most of the gain is: product images for a fast shop.
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| 2 |
If you also want to cache HTML, write the rule for public pages only (home, categories, products), passing straight to the origin when the request carries a session or cart cookie, with explicit exclusions for the paths in the table. How to write these rules differs from one CDN to another: follow your provider’s documentation.
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| 3 |
Check the origin’s headers: personal pages should go out with Cache-Control: private, no-store or equivalent. WooCommerce and the cache plugin usually take care of it; confirm with curl -sI, as in cache headers explained.
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| 4 |
Test with two browsers: in one, put a product in the cart; in the other, in a private window, open the cart: it must be empty. Log in on the first and check the second does not see your name.
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| 6 |
Repeat these tests every time you change a CDN rule or the cache plugin.
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A “cache everything” rule with no exclusions is the worst mistake you can make on a shop. If it happened and someone saw another person’s data: switch the rule off, purge the whole CDN, clear the site cache, and only then write the rule again with its exclusions. Similar symptoms without a CDN are covered in the WooCommerce cart empties by itself or shows the wrong items.
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When in doubt, do not cache HTML at the CDN. On a shop, the server’s page cache does that job and already knows the difference between a visitor with a cart and one without (LiteSpeed Cache: the first settings). Leave static files and protection to the CDN.
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The shop started misbehaving after you switched the CDN on? Tell us the address, which CDN you use and what rules you created.
Open a support ticket
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