How to Get Your Google Campaign Manager 360 API Key

In 2026, obtaining API access for Google's Campaign Manager 360 (CM360) requires navigating a complex process that emphasizes the use of OAuth 2.0 for authentication, specifically through service accounts for multi-tenant SaaS integrations. Unlike Google Ads, CM360 does not use API keys or a developer-token tier system, instead requiring Google's account team to enable API access at the account level. Each API call necessitates a userProfileId, which scopes the request and must be included in the URL path. The guide outlines steps for enabling the API in Google Cloud, creating service account credentials, and managing user profiles for each customer account. The service-account flow is recommended for multi-tenant SaaS, despite requiring manual setup for each customer, due to its stability and security advantages over user OAuth, which is more suited for single-tenant or internal tools. CM360's API structure maintains legacy DoubleClick naming conventions and demands careful management of service-account credentials and OAuth scopes to avoid common pitfalls like 403 errors. Additionally, Unified.to offers an alternative integration approach by providing a single API that abstracts away many of CM360's complexities, potentially easing the burden of maintaining direct integrations.

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