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Flexible Authentication System

1 post · Aug 2026

What this trail covers

This post details the evolution of Airbnb's authentication flows to a server-driven 'Identify first then Challenge' model. Key architectural decisions include a server-driven 'Challenge Picker' for fallback options and a fully server-driven screen abstraction. This has enabled faster experimentation, reduced client code, and improved user success rates, reduced duplicate accounts, and cut OTP costs.

All Airbnb trails
  1. Flexible Authentication: Reimagining authentication for millions of users at AirbnbThis post details the architectural decisions and results of rebuilding Airbnb's authentication flows using a server-driven 'Identify first then Challenge' model. It introduces the 'Challenge Picker' for fallback options and a fully server-driven screen abstraction, which decouples authentication strategy from client releases. The post highlights a 60% reduction in client code, a 100KB reduction in the web client bundle, an increase in successful authentications by 2.6%, a 27% reduction in duplicate accounts, and an 11% reduction in OTP costs.