Full Answer

Start by accepting what won't work: a browser-only pixel. On Safari the identifying cookie often expires before a typical consideration window closes, and the click ID that would rescue attribution is removed on cross-site navigation. Any approach that needs those two artefacts to persist in the browser will undercount Safari, which is frequently a fifth or more of a store's traffic.

The durable approach has three moving parts. First, capture the click identifier (gclid, fbclid, ttclid) on the very first server request, before Safari strips it, and persist it server-side against the session or order. Second, when the order completes, build the conversion event on your server with the value, currency, and a stable event_id. Third, send that event to each platform's conversions API, including hashed customer data so the platform can match it to the original click without a third-party cookie.

To avoid double counting, send the same event_id from both your pixel and the server so platforms deduplicate the pair. The result is conversion data that reflects what your server actually processed rather than what Safari allowed to survive. Browser signals still help where they exist, but the server becomes the source of truth, which is the only position Safari's privacy rules can't quietly erode.