How S2S tracking works
S2S tracking replaces the old cookie-and-pixel approach with a two-step handshake between servers:
- At click: your tracker generates a unique click ID and appends it to the offer URL — e.g.
https://offer.com/?cid=abc123. The offer's server stores that ID in its own database alongside the user session. - At conversion: when the user converts, the offer's server looks up the click ID, builds a postback URL, and fires a GET request back to your tracker — e.g.
https://tracker.com/p?cid=abc123&payout=25.
Your tracker receives the postback, matches abc123 to the original click, and logs the conversion with the reported payout. The user's browser, cookies, device, and IP address are all irrelevant to the attribution.
Why S2S beats cookie tracking in 2026
Traditional pixel/cookie tracking has been degraded by years of privacy changes:
- Safari ITP caps first-party cookies at 7 days and blocks third-party cookies outright
- iOS 14+ App Tracking Transparency forces opt-in prompts that gut mobile cookie tracking
- Ad blockers (uBlock, AdGuard, Brave) strip tracking pixels before they fire
- Chrome privacy sandbox continues phasing out third-party cookies
- Cross-device journeys — user clicks on phone, converts on desktop — kill cookie attribution entirely
S2S sidesteps all of this because the match happens on the advertiser's server, using an ID the user can't see or block. If the advertiser can identify the converting user, they can fire the postback — full stop.
S2S tracking vs pixel tracking
- Pixel: fires in the browser. Requires cookies, page load, and no blocker interference. Reliable for organic traffic, lossy for paid.
- S2S / postback: fires server-to-server. Requires the offer to support postbacks and pass through the click ID. Reliable regardless of traffic source or device.
Most serious affiliate trackers (Voluum, RedTrack, BeMob, FunnelFlux, Binom) run S2S by default and fall back to pixels only when an offer doesn't support postbacks.
Setting up S2S tracking
- Confirm the offer supports S2S / postbacks — not all in-house affiliate programs do
- Generate a unique click ID variable in your tracker (e.g.
{click_id},{sub1},{tid}) - Pass the click ID in your affiliate link via whichever parameter the offer accepts
- Copy your tracker's postback URL and paste it into the offer's conversion settings
- Run a test conversion end-to-end and verify the tracker records it with the correct click ID
Limitations of S2S tracking
It's not magic. S2S still breaks when:
- The click ID isn't stored by the offer (redirect strips it, session expires, user clears data mid-flow)
- The advertiser only fires postbacks in daily batches, creating attribution lag
- The postback URL is misconfigured — wrong macro syntax, missing parameters, HTTPS mismatch
- The advertiser decides to reject or claw back the conversion after the postback fires