Microsoft Advertising announced on April 1, 2026, a firm timeline for retiring its legacy SOAP API, setting October 1, 2026, as the date when all new features and enhancements will become available exclusively through the REST API. The SOAP API itself will be fully deprecated on January 31, 2027. Customers and partners have a 6-month window from the announcement date to migrate or at minimum plan their migration path.

The announcement, published by Eugene Goldenshteyn, Senior Product Marketing Manager at Microsoft Advertising, formalises a direction the company has been signalling since it introduced the Microsoft Advertising REST API in 2024. According to the blog post, the shift is part of a broader effort to build "a modern and scalable API platform that supports faster innovation and long-term growth."

What is actually changing, and when

Two dates define the migration schedule. From October 1, 2026, any new features or enhancements to the Microsoft Advertising API will be available only through the REST API. Existing SOAP-based integrations will continue to function during the transition period - there is no immediate disruption to current workflows. Then, on January 31, 2027, the SOAP API reaches full deprecation. After that date, the legacy interface will no longer be supported.

The 6-month runway to the October cutoff - and roughly 10 months to the January 2027 deadline - gives integrators time to assess their dependencies, update code, and validate changes in staging environments before live campaigns are affected.

Why SOAP is being retired

SOAP (Simple Object Access Protocol) is an XML-based messaging protocol that became widely adopted in enterprise software in the early 2000s. Microsoft's advertising API relied on it for years, making it deeply embedded in many third-party integrations, agency tools, and custom advertiser platforms. REST (Representational State Transfer), by contrast, uses standard HTTP and JSON - lighter, faster to parse, and far better supported by modern programming languages and frameworks.

According to the announcement, the Microsoft Advertising REST API is designed to deliver "a more modern, scalable, and consistent integration experience." The listed benefits include access to new and future API features, stronger SDKsupport, standard HTTP/JSON architecture, easier integration and debugging, and broader programming language support. These are not abstract advantages. Developers who have worked with both protocols typically find REST significantly quicker to implement and troubleshoot, partly because most web development tooling is built around HTTP by default.

The move also signals that Microsoft will invest its API development resources entirely in the REST layer going forward. Once October 1, 2026 passes, any advertiser or partner still on SOAP will not gain access to new capabilities - a meaningful competitive disadvantage for anyone running complex automated campaigns or building products on top of the Microsoft Advertising platform.

Migration paths: SDK users vs direct integrations

Microsoft has laid out two distinct migration tracks, depending on how the SOAP API is currently being used.

For SDK users - those integrating via Microsoft's official software development kits - the path involves following SDK migration documentation, which Microsoft says is designed to simplify the move from SOAP to REST and keep implementations aligned with future updates. Using an SDK abstracts much of the raw HTTP work, reducing the volume of code changes needed.

For non-SDK users who call the SOAP API directly, the migration requires updating implementations to use REST API URLs and the JSON request format. The correct REST endpoints and request examples for each method are available in Microsoft's API reference documentation. Microsoft also notes that this migration is an opportunity to move to an SDK if one is not already in use, which would make future updates easier to handle.

For complex integrations that need additional time, Microsoft's announcement points to account teams and Microsoft Advertising support as contact points for discussing extended migration plans.

Context: a pattern of infrastructure consolidation

The SOAP retirement does not happen in a vacuum. It fits a clear pattern in how Microsoft has been consolidating its advertising infrastructure over the past two years.

Microsoft retired its mobile advertising app in January 2026, removing a standalone application that had been available on the Apple App Store and Google Play. The company cited a strategic shift toward web-based management interfaces, directing users to browser-based access instead. Microsoft sunset its Xandr DSP in May 2025, announcing it would discontinue Microsoft Invest (formerly AppNexus) effective February 28, 2026, describing the move as a focus shift toward conversational and agentic advertising. The Bing Search API was retired in August 2025, another deprecation in the same period of platform rationalisation.

Each of these moves reduces the surface area of legacy systems Microsoft needs to maintain, while pushing integrators toward newer infrastructure. The SOAP-to-REST migration follows that same logic. Rather than running two API surfaces indefinitely, Microsoft is consolidating on REST and setting a hard deadline.

How this compares to API deprecations at other platforms

The advertising technology industry has seen a wave of API lifecycle changes in recent years, and the timelines vary considerably. Google moved its Ads API to monthly releases starting January 2026, accelerating feature delivery in response to developer feedback. Google's approach there was additive - shipping faster - whereas Microsoft's SOAP retirement is subtractive, removing a legacy layer.

Meta has also been running a structured API deprecation programme, releasing Graph API v21.0 and Marketing API v21.0 in October 2024 with a published schedule of version retirements. In that context, Microsoft's two-date framework - feature lock on October 1, 2026, full shutdown on January 31, 2027 - is relatively straightforward and gives more lead time than some Meta API deprecations have provided.

Amazon, meanwhile, has been consolidating its own DSP inventory management APIs into a unified framework under Amazon Ads API v1, announced in March 2026. The industry direction is consistent: major platforms are pruning legacy interfaces and standardising on modern HTTP-based architectures.

Who is affected and what the stakes are

The primary audience for this announcement is developers and technical teams who have built or maintain integrations with the Microsoft Advertising API. This includes third-party bid management platforms, agency campaign management systems, custom advertiser tooling, and any automation scripts that call the SOAP endpoint directly.

For advertisers who use Microsoft Advertising through the web interface or through tools that abstract the API layer - such as Microsoft Advertising Editor or Google Import - there is no direct action required. The migration burden falls on the integration layer, not on the campaign itself.

That said, the downstream effect on advertisers is real. If a third-party tool used for campaign management has not migrated by October 1, 2026, it will stop receiving new Microsoft Advertising features. Advertisers dependent on such tools should check with their vendors about migration timelines.

Microsoft's advertising revenue crossed $20 billion annually by April 2025, driven substantially by Copilot integration and AI-powered features. Much of that feature velocity - Image Animation, Performance Comparison tools, expanded API access for generative AI capabilities - was delivered in November 2025 via the REST API pathway. Staying on SOAP after October 2026 means forgoing all of that going forward.

Technical implications of the REST architecture

The shift to REST has concrete technical implications beyond the surface-level change in protocol. JSON payloads are generally smaller than the equivalent XML in SOAP, which reduces bandwidth usage for high-volume API calls - relevant for large accounts making frequent bid or budget updates. HTTP caching is also natively supported in REST, allowing intermediary systems to cache responses where appropriate, whereas SOAP typically uses POST for all operations, bypassing standard HTTP cache semantics.

Error handling also differs. SOAP returns SOAP faults as XML envelopes, which requires XML parsing to extract error details. REST APIs return HTTP status codes alongside JSON error bodies, making errors easier to parse with standard libraries in most languages. For teams managing large-scale integrations across multiple platforms, aligning on a single paradigm - HTTP/JSON - also reduces the cognitive overhead of switching between different integration styles.

Stronger SDK support, cited in Microsoft's announcement, reflects the reality that most modern API SDKs are built around REST. SOAP SDKs are less actively maintained across the ecosystem, and finding up-to-date client libraries for less common programming languages has become increasingly difficult. The REST migration also positions Microsoft's API surface for compatibility with tools and frameworks that did not exist when SOAP was dominant, including those built around AI-assisted development workflows.

What the marketing community should watch

For marketing technology professionals, the October 1, 2026, and January 31, 2027, dates are the key planning anchors. Any platform or tool used to manage Microsoft Advertising campaigns programmatically needs to be assessed against these dates. The questions are: does it use the SOAP API, is the vendor planning a migration, and by when?

Microsoft's pattern of infrastructure consolidation over the past 18 months - mobile app retirement, DSP shutdown, Bing Search API retirement, and now SOAP deprecation - suggests that the January 2027 deadline is firm. There is no indication in the announcement that extensions will be available as a default; extended migration plans are described as a conversation with account teams, not a general option.

The REST API's arrival in 2024 and the features subsequently built on it make the destination clear. The SOAP API served its purpose for well over a decade. The industry has moved. The question now is whether integrations built on it are ready to move too.

Staying informed and next steps

Microsoft is directing integrators to its API reference documentation for REST endpoint details and request examples for each method. SDK users have dedicated migration documentation. For teams with complex setups, Microsoft's account teams and Microsoft Advertising support are identified as the channels for discussing extended migration planning. The company also runs the Microsoft Advertising Insider newsletter, which it recommends as a source for product updates during the transition period.

The practical first step for any team with SOAP-based integrations is to inventory where SOAP calls are made - whether inside proprietary tools, agency platforms, or direct integrations - and to map each call to its REST equivalent. Microsoft's reference documentation lists the correct REST endpoints and request examples per method. For SDK users, the SDK migration documentation provides a guided path. Neither path is described as especially disruptive for standard integrations, though highly customised SOAP implementations may require more significant refactoring.

What matters most for the marketing community is that the clock started on April 1, 2026. Six months to October 1, 2026, is a workable timeline for straightforward integrations. For larger organisations with multiple teams, vendor dependencies, and custom automation built over years, the window is narrower than it appears. Platform changes of this kind tend to surface legacy dependencies that were not visible until migration is underway. Starting the assessment now, rather than in September, is the practical response to a firm deadline.

Timeline

Summary

Who: Microsoft Advertising, affecting developers, agencies, third-party platform vendors, and advertisers using programmatic integrations with the Microsoft Advertising API.

What: Microsoft is retiring its legacy SOAP API in favour of the REST API. From October 1, 2026, new features will be exclusive to REST. The SOAP API will be fully deprecated on January 31, 2027. Existing SOAP integrations continue to run during the transition period.

When: Announced April 1, 2026. Feature lock for SOAP: October 1, 2026. Full deprecation: January 31, 2027.

Where: Affects all programmatic integrations with the Microsoft Advertising API globally, across all markets and account types that use the SOAP-based interface.

Why: Microsoft is standardising on REST as the foundation for future API development, citing a modern HTTP/JSON architecture, stronger SDK support, broader programming language compatibility, and easier integration and debugging compared to the legacy SOAP protocol.

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