Glossary · Tracking & Attribution

What is S2S Tracking?

Definition

Server-to-server tracking, in which conversions are reported directly between servers using a stored click ID instead of browser cookies or pixels.

S2S (server-to-server) tracking is a conversion-tracking method in which the advertiser's server reports conversions directly to the tracking platform, usually by calling a postback URL with a click ID. Nothing has to load in the user's browser at the moment of conversion, so attribution survives ad blockers and cookie restrictions, and works for conversions that happen days later or on another device.

How it works

S2S tracking has two halves: passing the click ID forward and sending it back.

  • Forward: the tracking link redirects the user to the advertiser's site with a unique click ID appended, for example ?click_id=abc123.
  • Storage: the advertiser saves the click ID with the session, lead, or user account.
  • Back: when the conversion happens, the advertiser's backend sends an HTTP request to the tracker's postback endpoint containing the click ID, event type, and amount.

Because the click ID is stored with the account, a user who signs up on mobile and deposits later on desktop can still be attributed.

Example

A simplified S2S flow for a lead-generation offer (illustrative URLs):

1. Click:     https://track.example.com/c/123?sub1=fb_campaign_7
2. Redirect:  https://brand.example.com/signup?click_id=abc123
3. Postback:  https://track.example.com/postback?click_id=abc123&event=lead&amount=12.00

The tracker matches abc123 to the original click, credits the affiliate, and attaches sub1=fb_campaign_7 to the conversion for reporting.

Why it matters

For brands, S2S tracking produces cleaner data and can report events that happen long after the click, such as KYC approval or a first deposit. It is also harder to spoof than a browser pixel when the endpoint is protected with a secret token or IP allowlist. For affiliates, it means fewer lost conversions and reliable data for optimizing traffic. The trade-off is setup: the advertiser must capture and store the click ID correctly.

MassPartner offers S2S postbacks for brands, with an installation tester in the brand dashboard. See how postback URLs work for a step-by-step setup.

Related: postback URL, click ID, pixel tracking, Conversions API.

Related terms

  • Postback URL

    A URL one system calls server-to-server to report a conversion to another, passing the original click ID plus details such as payout and status.

  • Click ID

    A unique identifier generated for each click on a tracking link or ad, used to match later conversions back to that exact click.

  • Pixel Tracking

    Client-side conversion tracking in which a tag or tiny image on the confirmation page fires in the user's browser and reports the conversion.

  • Conversions API

    A server-side interface for sending conversion events from an advertiser's server directly to an ad platform, best known from Meta's Conversions API.

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