minimothMiniMoth vs Firebase Phone Auth: OTP Pricing for Indian Developers
21 August 2026
Firebase Phone Authentication is the default choice for a lot of India-first apps — it’s already in the SDK if you’re using Firebase for anything else, and setup takes minutes. The catch shows up in the bill once you’re past the testing phase: phone auth in Firebase is metered per SMS through Google Cloud’s Identity Platform pricing, and India isn’t a discounted tier.
The actual numbers
| Per OTP (India) | Free tier | |
|---|---|---|
| MiniMoth | ₹0.35 | ₹20 for 3 months (~57 OTPs) |
| Firebase Phone Auth | ≈₹6 | 10 SMS/day, test phone numbers only |
Google Cloud’s Identity Platform pricing page lists India (IN) at $0.07 per SMS verification — at current exchange rates ($1 ≈ ₹83.2, per the Federal Reserve’s August 2026 rate), that’s about ₹6 per OTP. The 10-free-SMS-per-day allowance only applies to Firebase’s SIM-less test mode with test phone numbers registered in the console — it doesn’t cover real user traffic, and phone auth has required a Blaze (pay-as-you-go) billing account attached to the project since September 2024.
At 1,000 OTPs a month, that’s roughly ₹350 on MiniMoth versus ≈₹6,000 on Firebase.
Why the gap exists
Firebase Authentication is a full identity platform — phone OTP is one sign-in method among many (email/password, social login, anonymous auth, MFA), and SMS delivery is billed through the same general-purpose Identity Platform pricing regardless of which country you’re sending to. DLT compliance (the TRAI-mandated sender and template registration required to send SMS to Indian numbers) isn’t part of what Firebase handles — the messages arrive from a Google-controlled sender, not a registered entity of yours, so you have limited control over sender identity and no DLT paperwork to point to if a carrier or client asks.
MiniMoth only does one thing: phone OTP for Indian numbers. It’s TRAI DLT-registered directly, sends OTP via WhatsApp first (which doesn’t require DLT registration at all, since it goes through Meta’s Cloud API) and falls back to SMS automatically if WhatsApp fails. You’re not charged for an OTP that wasn’t delivered on either channel — the charge is reversed automatically to your credits balance if both channels fail, unless the number shows a recent pattern of repeated delivery failures.
What you don’t have to build
Beyond price, the OTP-specific parts of MiniMoth’s API save you from building:
- Rate limiting per phone number (send and verify)
- Session management with access + refresh token rotation
- DLT sender registration and carrier approval paperwork
- WhatsApp-first delivery with automatic SMS fallback
If you’re using Firebase for everything else (Firestore, hosting, other sign-in methods) and only want to swap the OTP/SMS piece for Indian numbers, MiniMoth’s REST API is two endpoints — POST /v1/otp/send and POST /v1/otp/verify. And if you’d rather keep Firebase’s own auth state and just want MiniMoth to confirm the phone number, see the Firebase integration guide for minting a Firebase custom token from a MiniMoth-verified session — that’s the opposite direction from this comparison, for teams who want to keep Firebase Auth and only change how the SMS gets sent.
See the full pricing breakdown or the quickstart to send your first OTP.