Full Answer

Client-side tracking depends on a browser loading a page with a tracking script. The initial subscription purchase follows the normal checkout flow — the visitor clicks buy, lands on the order-received page, and the GA4 purchase event fires. But every subsequent renewal is processed by the payment gateway (Stripe, PayPal, or the WooCommerce cron job) without any browser session. No browser session means no JavaScript execution, which means no GA4 event, no Meta pixel, and no Google Ads conversion tag.

The downstream damage compounds. Ad platforms optimise toward the signals they receive — if they only see first purchases, they optimise for acquisition, not retention-quality customers. A subscriber who churns after one month and one who stays for two years look identical to Google Ads, because only the first transaction was visible. That's not a reporting gap; it's a misalignment of the algorithm's entire optimisation target.

Server-side event tracking closes the loop by capturing renewal events directly from the payment webhook or WooCommerce action hook — no browser required. Each renewal, upgrade, and cancellation becomes a trackable event that can feed GA4 Measurement Protocol, Meta CAPI, and BigQuery for lifetime-value analysis ([WooCommerce tracking](https://seresa.io/blog/woocommerce-tracking/)).