СAPI stands for conversion API and is designed to enable passing marketing data from publishers to ad platforms smoothly, server-side.
The Story Behind
While the notion of conversion APIs isn’t new, the market interest in their adoption has increased over the past several years, in view of the gradually limiting capabilities to track conversions using browser-based methods.
Unlike these, the use of CAPI allows tracking conversions (e.g. clicks, registrations, finalized purchases, and more), passing this information from a publisher to an ad platform and, consequently, making it available for advertisers, in a more transparent and privacy-preserving way. This helps brands to measure ROI and other ad KPIs more precisely and get a better understanding of the actual effectiveness of their online advertising campaigns.
Barriers to CAPI Adoption
While the benefits of implementing CAPI seem obvious for all parties in the digital advertising ecosystem, a major barrier to adoption persists as of 2025 – it’s the lack of a relevant industry-wide standard.
The fact is, while the top-tier ad platforms, including Google, TikTok and Meta, just to name a few, have been offering their proprietary CAPI solutions for quite some time now, each of these implies different templates on how the conversion event data is being labeled and passed. This makes the technical implementation trickier, than it could be, if a unified standard was available on the market. Fortunately enough, IAB Tech Lab has announced the draft tech specification is already in development.
Another challenge that digital businesses using CAPI might face is related to the actual technical implementation process, which requires either the deep knowledge of S2S integrations or a significant financial investment, in case a third-party vendor handles it.
More importantly, the ongoing performance monitoring and data quality assurance are also crucial to ensure desired outcomes in the medium- and long-term perspective, which inevitably require extra time and operational effort.
Nonetheless, despite the existing challenges and limitations, most experts admit the use of conversion APIs will only expand in 2026 and beyond.