🔐 How OTP Autofill Actually Works (Deep Dive for Developers)

Have you ever wonder how this "OTP Auto filling " Works. OTP auto-filling looks “magical”, but it’s actually a combination of OS-level SMS parsing + app/browser integration + security rules. Let’s break this down properly — Android, iOS, and Web — from a developer’s perspective. 🧩 The High-Level Flow At a system level, OTP autofill follows this lifecycle: User enters phone number. Backend generates OTP. SMS gateway delivers OTP. OS intercepts and parses the message. If conditions match → OTP is surfaced to app/browser. App auto-fills (or suggests) the code. The key insight: Apps do NOT automatically read all your SMS messages.The operating system controls everything. 📱 Android OTP Autofill (Deep Dive) You request OTP You enter phone number in an app (like WhatsApp, Paytm, etc.) Server generates OTP → sends SMS via SMS gateway. SMS arrives on your phone Your OTP is 482913. Do not share it. AppName: 9xYz12AbC Android / iOS detects OTP automatically The operating system scans incoming SMS