Google last week announced that starting June 15, 2026, the Google Ads API will stop accepting new adopters of offline conversion imports, including enhanced conversions for leads. The change, published on May 15, 2026, on the Google Ads Developer Blog by Ben Karl on behalf of the Google Ads API Team, marks the latest in a sequence of restrictions that have been progressively narrowing the scope of the Google Ads API in favour of the newer Data Manager API.

The cutoff and what triggers it

The deadline is June 15, 2026. After that date, developers who have not already adopted offline conversion imports - or who have not imported offline conversions between December 2025 and May 2026 - will receive an error when they attempt to use the ConversionUploadService.UploadClickConversions method. According to the developer blog post, the specific error returned will be CUSTOMER_NOT_ALLOWLISTED_FOR_THIS_FEATURE. The enforcement mechanism works at the developer token level: Google will maintain an allowlist of developer tokens that have demonstrated prior use, and new attempts from tokens outside that list will be rejected outright.

Developers who have already adopted offline conversions or enhanced conversions for leads are not cut off immediately. They can continue using the Google Ads API for imports while they carry out their integration with the Data Manager API. The message is clear though - continued access via the older path is explicitly framed as transitional.

The announcement states that the Data Manager API is now the primary API for importing offline conversions. This is the same framing Google has used in its previous migration announcements covering session attributes and IP address data, as well as Customer Match.

What is being restricted

Offline conversion imports allow advertisers to send data about conversions that happen outside of a web session - such as a phone call that closes a deal, a CRM record that marks a lead as won, or an in-store purchase - back to Google Ads, where it gets matched against prior ad interactions. This attribution mechanism is widely used in B2B advertising and retail, where the moment of purchase is separated from the moment a user clicks an ad.

Enhanced conversions for leads extend this approach. They were launched in March 2022 and allow advertisers to upload hashed first-party identifiers - primarily email addresses or phone numbers - from CRM systems to Google Ads. Google then matches those against hashed data associated with signed-in Google Accounts, allowing it to tie offline outcomes back to specific ad clicks. PPC Land documented the technical distinctions between enhanced conversions for web and enhanced conversions for leads in January 2024, noting that the leads variant typically delivers higher matching accuracy because the matching process is more direct, though it requires additional CRM data setup.

Both of these mechanisms - standard offline conversion imports and enhanced conversions for leads - are now subject to the June 15 restriction for any developer token that cannot demonstrate active use between December 2025 and May 2026.

The Data Manager API as replacement

The Data Manager API was formally launched on December 9, 2025, with eleven launch partners. According to the PPC Land coverage of that launch, the API operates via both REST and gRPC protocols. It supports three primary data categories: audience members using Customer Match, mobile device identifiers and Publisher Advertiser Identity Reconciliation identifiers, and conversion data. Within conversions, it handles offline conversions, enhanced conversions for leads, and conversion events that serve as supplementary signals for tag-based tracking. Each Google Cloud project is limited to 100,000 requests per day and 300 requests per minute, with individual requests supporting up to 10,000 audience members or 2,000 conversion events, and up to 10 user identifiers per record.

Authentication uses OAuth 2.0 with the datamanager scope, which is distinct from the scopes used by the Google Ads API. Developers integrating with the Data Manager API for the first time will need to configure new credential flows.

The unified schema is one of the architectural differences with practical implications. According to PPC Land's April 2026 analysis of the Data Manager API, the old architecture required separate field names and requirements for each Google product. A transaction ID could carry subtly different semantics depending on which product pipeline it was sent to. The Data Manager API enforces one schema across Google Ads, Google Marketing Platform, and Google Analytics. That consistency also reduces the cost of adding additional use cases once the initial integration is in place - a team already sending offline conversion data through the new API can add offline conversion adjustments or enhanced conversions for web without redesigning the endpoint logic.

The API has continued to expand since its December launch. Version 1.6, released in May 2026, added store sales measurement and expanded Analytics event support. Store sales conversions previously required managing multiple offline upload jobs. The updated API handles those through the same endpoint structure used for other conversion types. Version 1.0 supported only audience data for Google Ads and Display and Video 360. Version 1.1 added offline conversion event ingestion. Version 1.2 extended that to enhanced conversions for leads. The product has moved quickly.

A pattern of sequential restrictions

The June 15 deadline for offline conversion imports follows the same structural pattern as two earlier migration deadlines. On February 2, 2026, the Google Ads API stopped accepting new adopters for session attributes and IP address data in conversion imports. PPC Land reported on that change in January 2026, noting that both session attributes and IP addresses had served as attribution signals, helping advertisers understand geographic patterns and validate conversion authenticity.

Then on April 1, 2026, the Google Ads API stopped functioning for Customer Match uploads via OfflineUserDataJobServiceand UserDataService. Google had notified developer token holders of that deadline on March 4, 2026, leaving approximately four weeks for developers to complete their migrations or risk broken pipelines.

In each case, the Google Ads API continued to serve developers who had already integrated, while closing the door to new adopters and eventually full usage. The offline conversion import restriction announced today follows the same two-phase approach: new adopters blocked first, with existing users given time to migrate before a fuller cutoff.

Technical implications for developers

Developers building or maintaining integrations that use ConversionUploadService.UploadClickConversions need to assess their token's status against Google's allowlist criteria. The qualifying condition is prior use between December 2025 and May 2026. Tokens that fall outside that window and attempt to upload after June 15 will receive the CUSTOMER_NOT_ALLOWLISTED_FOR_THIS_FEATURE error, at which point the upload will fail silently from the advertiser's perspective unless the calling system has explicit error handling for that response code.

Google has published a migration guide specifically for Google Ads API users moving to the Data Manager API for offline conversions. The guide is referenced in the developer blog announcement. Support channels for both the Google Ads API and the Data Manager API are available for questions, and Google has directed developers to the "Google Advertising and Measurement Community" Discord server for broader discussion.

The Google Ads API Developer Assistant v2.0, released in March 2026, added diagnostics tools specifically for offline conversion tracking. Those tools are designed to help developers trace failures across customer settings, conversion action configurations, and upload job summaries - a toolset that will remain relevant during migrations where both the old and new pipelines may be active simultaneously.

Broader measurement consolidation

The offline conversion migration is happening alongside other changes to how Google structures conversion data flows. In April 2026, Google Ads began accepting user-provided data simultaneously from website tags, Data Manager, and API connections, removing the previous requirement to select a single implementation method. That change lowered the operational risk for teams migrating gradually.

Google also announced in April 2026 that enhanced conversions for web and enhanced conversions for leads will merge into a single toggle starting in June 2026, removing the structural split that has existed since the leads variant launched in 2022. Advertisers will no longer need to configure two separate features - a unified status indicator with a single on/off setting will replace them. That change arrives in the same month as the Data Manager API restriction for new offline conversion adopters.

Google Tag Manager has also moved inside the Google Ads Data Manager interface, allowing advertisers to manage tags without leaving the ads platform. That integration was observed by practitioners in early May 2026 and is rolling out gradually across accounts.

The cumulative effect of these moves is a measurement infrastructure that routes a larger share of first-party data through the Data Manager API, with the legacy Google Ads API path being progressively narrowed. For marketing technology vendors and agencies managing multiple advertiser integrations, the migration to the Data Manager API is no longer a future consideration - three separate enforcement deadlines have passed since February, and a fourth arrives in June.

Timeline

Summary

Who: Google's Ads API Team, targeting developers and marketing technology providers who use developer tokens to upload offline conversion data via the Google Ads API's ConversionUploadService.

What: Starting June 15, 2026, the Google Ads API will no longer accept new adopters of offline conversion imports, including enhanced conversions for leads. Developers outside the allowlist - defined by active use between December 2025 and May 2026 - will receive the error CUSTOMER_NOT_ALLOWLISTED_FOR_THIS_FEATURE when calling ConversionUploadService.UploadClickConversions. The Data Manager API is now the designated replacement for all offline conversion ingestion.

When: The announcement was published on May 15, 2026. The enforcement deadline is June 15, 2026. Existing adopters can continue using the Google Ads API while they migrate.

Where: The change affects the Google Ads API specifically, with the Data Manager API as the designated replacement. The announcement was published on the Google Ads Developer Blog by Ben Karl.

Why: Google is consolidating first-party data ingestion into the Data Manager API, which enforces a unified schema across Google Ads, Google Marketing Platform, and Google Analytics. The offline conversion restriction is the third in a series of sequential cutoffs - following session attributes and IP address data in February 2026 and Customer Match in April 2026 - that together shift the primary data pipeline away from the older Google Ads API infrastructure.

Share this article
The link has been copied!