Server-to-Server (S2S) Tracking

Server-to-server (S2S) tracking — also called postback tracking — moves conversion reporting off the browser and onto the server. When a sale completes, the advertiser's backend sends an HTTP request straight to the tracking platform carrying the click ID that identifies the originating click. Nothing depends on the visitor's browser loading a tag, so S2S is immune to ad blockers, third-party cookie blocking, and funnels that cross domains between click and conversion.

How the chain works

1. A visitor clicks a tracking link and the platform mints a click ID, appending it to the destination URL (e.g. ?ll_cid=abc123).
2. The advertiser captures that click ID and stores it alongside the order or lead in their own system.
3. When the conversion fires, the advertiser's server sends a postback to the tracking domain including that click ID.
4. The platform matches the click ID to the recorded click and credits the right affiliate.

The one thing S2S requires is that the click ID makes the round trip — captured at click, echoed at conversion.

A worked example

A lead-gen advertiser runs a multi-step funnel: the ad lands on signup.brand.com, but the application completes on apply.brand.com, a different domain. A browser conversion pixel would struggle here because the thank-you page's cookies live on a different site. With S2S, the advertiser simply stores ll_cid=abc123 when the visitor first arrives, then fires from their server when the application is approved:

POST https://track.yourbrand.com/conv
          ll_cid=abc123  txn=app-5521  event=3  email=jane@example.com
        

Because it is a POST, the email travels in the body, not the URL — the right way to send personal data.

S2S vs pixel tracking

Pixels are simpler to deploy and fine for a single thank-you page on one domain. S2S is more robust and more private, and it is the only reliable option for delayed conversions (a lead approved days later), cross-domain funnels, or anywhere the browser can't be trusted to fire a tag.

How this works in LimeliJourney

LimeliJourney's tracking treats S2S as a first-class path: the Conversion Pixel tab hands you a copy-paste server-to-server example next to the image and iframe variants, with the IDs already filled in. Add &format=json and the fire returns a JSON acknowledgement — conversion ID and status — you can log in your CRM. Send a transaction ID so retries are idempotent, and pass ll_cid to anchor attribution to the exact click. For conversions with no click ID, fallback IDs (aff, cmp) still credit the right affiliate. Every fire is auditable in the Pixel Log.