What Is an API Aggregator? A 2026 Developer's Guide

In 2026, the concept of an "API aggregator" encompasses three primary interpretations: fintech intermediaries like Plaid and Tink for banking APIs under regulations such as PSD2, SaaS integration products like Apideck and Unified.to that consolidate multiple SaaS APIs into a unified interface, and a generic architectural pattern in which a backend service aggregates calls to multiple APIs into a single response. The guide primarily focuses on the second category, where an API aggregator simplifies B2B SaaS integrations by providing a single API endpoint to access various third-party services, such as CRM or HRIS systems, through normalized data models, credential management, and request routing. While the terms "API aggregator" and "unified API" are often used interchangeably in SaaS contexts, "unified API" is the more modern term emphasizing consistent schema and semantics. The discussion also differentiates between API aggregators and related concepts like API gateways and iPaaS, clarifying their distinct roles and functionalities. Unified.to is highlighted as a comprehensive unified API option, offering real-time pass-through architecture and compliance with various data protection regulations, alongside other providers like Merge and Kombo, each with unique architectural approaches.