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Introduction

If you already have a live Retail Media integration, you are close to running Offsite campaigns. The Offsite Add-on reuses your existing setup, product feed, API calls, and onsite events, and adds one new piece: an identification call that links your first-party user ID to Criteo’s identity graph. /fpm/init is that identification call. It associates your first-party visitor ID (RVI) and your retailer account with Criteo’s internal identifiers, so the Retail Media events you already send become available for Offsite targeting and measurement.

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Prerequisites

  • Your onsite Retail Media solution is live and delivering ads.
  • You have a stable first-party user identifier (RVI).
  • The identification call must be triggered from the browser (not server-side).
  • You have received from your Criteo representative:
    • Retailer ID (retailer_id)
  • On every identification call you pass (all required):
    • first_party_id: your stable RVI (same value as in your Retail Media integration)
    • retailer_id: Criteo-issued retailer identifier
    • first_party_name: friendly name for your retailer or site (used in logs and diagnostics)

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Concept definitions

  • Onsite: ads rendered on your site or app using your first-party traffic.
  • Offsite: ads delivered outside your site, using your first-party data to reach shoppers on external inventory.
  • RVI (Retailer Visitor ID): your stable, persisted first-party identifier for a visitor. Use it as first_party_id in calls to /fpm/init.

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Retail Media API events (full_url)

The Offsite add-on reuses the Retail Media API events you already send. In addition to the /fpm/init identification call, confirm that those event calls include full_url set to the full page URL where the event occurred (for example https://shop.example.com/path?query=1), not only the domain (for example shop.example.com). Many integrations send the domain alone; that is not sufficient for Offsite via this flow. Audit your payloads before go-live and validate with your Criteo contact in staging. You should apply privacy by design: when the user has not granted consent, your site must not load third-party tags, including the Criteo Offsite identification call to https://gum.criteo.com/fpm/init. Only when consent for Criteo is granted should that call be triggered. Make sure you have a solution in place that controls whether the Criteo call runs (for example your CMP, tag manager, or equivalent). If consent is not granted, the Criteo Offsite call must not run at all. If consent to Criteo is granted, then trigger the Offsite identification call. If you do not have such a solution in place, contact Criteo support, we can help you implement Criteo’s solution for handling consent alongside this integration. Note: This guide does not document Criteo’s server-side consent evaluation in detail. Customer-facing guidance is to gate the call on the client unless Criteo has agreed a different pattern with you. Query keys such as gdpr, gdpr_consent, us_privacy, gpp, and gpp_sid are intentionally omitted from this guide.
Browser-only, cookies, and fetch — /fpm/init must be triggered from the browser. Criteo relies on cookies and probabilistic signals only available in a browser context to complete identity resolution. Server-side calls alone will not work. Fire the call on every page load where your RVI is available, not just once per session. When using fetch, pass credentials: "include" so cookies can be sent on cross-site requests (same intent as xhr.withCredentials = true).

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Endpoints Overview

VerbEndpointDescription
GEThttps://gum.criteo.com/fpm/initIdentification call that links your first-party visitor ID (RVI) to Criteo’s identity graph for Offsite activation.
POSThttps://gum.criteo.com/fpm/initSame as GET. Parameters are passed in the query string.

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Attributes

Required query parameters (confirmed with R&D): retailer_id, first_party_id, and first_party_name. This guide documents only these three for the standard Offsite add-on flow.
AttributeData TypeDescription
first_party_id *stringYour first-party visitor ID (RVI). Must be stable and consistent across calls; use the same value as in your existing Retail Media integration. Accepted values: non-empty string. Writeable? Y / Nullable? N
retailer_id *stringYour retailer identifier in Criteo systems. Provided by Criteo. Accepted values: Criteo-issued retailer ID. Writeable? Y / Nullable? N
first_party_name *stringFriendly name for your retailer or site (used in logs and diagnostics). Accepted values: non-empty string. Writeable? Y / Nullable? N
*Required Parameters not listed here: Query keys such as gdpr, gdpr_consent, us_privacy, gpp, and gpp_sid are intentionally omitted from this guide. The documented integration uses client-side consent gating only (see Consent section above). Do not add other query fields unless Criteo Support gives you a written custom specification.

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FPM identification call (/fpm/init)

Links your RVI and your retailer account to Criteo’s identity graph for Offsite activation. HTTP METHOD: GET (POST also supported; parameters remain in the query string). Full URL: 
https://gum.criteo.com/fpm/init
Sample Request 
curl -L -X GET 'https://gum.criteo.com/fpm/init?first_party_id=<YOUR_RVI>&retailer_id=<YOUR_RETAILER_ID>&first_party_name=ShopExample' \
-H 'Accept: */*' \
-b cookies.txt -c cookies.txt

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Responses

ResponseTitleDetailTroubleshooting
🟢 200Call executed with successYour request succeeded. The server responded as required for this step.Confirm you made the call from the browser with redirects enabled and credentials/cookies allowed. If identification still fails, check for the expected Criteo cookies in the response with your Criteo contact.
🔴 400Bad requestThe server could not process the request (e.g. malformed URL, invalid or missing required parameters, or bad encoding).Review your query parameter names and values: required fields first_party_id, retailer_id, and first_party_name; correct URL encoding.