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First-party attribution uses data you collect and control from your own properties (your site/app and checkout) to understand which marketing touchpoints contributed to purchases. In practice, this typically includes First-Party Inputs from multiple sources:
  • Website Events: pixel-based tracking (e.g., GA4, Elevar)
  • Server-Side Capture: API-based tracking (e.g., Shopify Order Attributes, Connectors)
  • Landing Page Data: Referrer and URL parameters captured at the start of the session
SourceMedium aggregates all these First-Party Inputs to build a complete picture.

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First-party vs platform-reported attribution

  • First-party: derived from your site/app + checkout signals (what happened on your properties)
  • Platform-reported: derived from ad platforms (what platforms believe happened based on their measurement and models)
Both can be useful; they often differ due to attribution windows, privacy restrictions, and identity resolution.

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What counts as a first-party signal in SourceMedium

Common examples include:
  • Website analytics/event streams (e.g., GA4, Elevar)
  • Landing page + referrer capture (including UTMs when present)
  • Checkout/order-level capture for UTMs (useful when browser tracking drops parameters)

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Where first-party attribution shows up in SourceMedium

  • Last-click attribution (UTM-based): relies on UTMs/landing/referrer capture to assign the most recent touchpoint.
  • Multi-touch attribution (MTA): uses first-party purchase journeys (touchpoints) to model first touch, last touch, and linear attribution across the journey.

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Common failure modes (and how to reduce them)

  • (direct) / (none) growth: usually missing UTMs or UTMs being dropped during the journey (cross-domain/checkout).
  • Cross-domain/checkout breaks: customers move between domains or checkout flows and attribution context is lost.
  • Browser/privacy restrictions: ad blockers, iOS privacy features, and browser changes reduce client-side tracking reliability.
Start with consistent UTM setup, then ensure you are capturing data across both client-side (pixel) and server-side (API) inputs to maximize coverage.

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External resources

UTM Setup

What UTMs are and how to implement them across channels.

Attribution Health

Find and fix tracking gaps that reduce first-party coverage.

MTA Overview

How SourceMedium builds multi-touch attribution from first-party purchase journeys.

GA4 Common Failures

Troubleshoot common analytics issues that impact event-based attribution.

Backfilling UTM Attribution via Order Attributes

Shopify Plus developer guide for capturing UTMs at checkout.