SMS Backends

Built-in backends

Backend	Use case	Extra dependency
ConsoleSmsBackend	Development — prints to stdout	none
TwilioSmsBackend	Twilio	none (uses httpx)
AWSSNSSmsBackend	AWS SNS	boto3 — install via pip install "authwarden[sns]"

Unlike email, there's no sms_backend config selector field — only credential fields (twilio_account_sid, etc.) exist on WardenConfig. You always build and pass the SMS backend instance directly.

Twilio

from authwarden.sms.twilio import TwilioSmsBackend

warden = AuthWarden(
    config=config,
    user_store=store,
    sms_backend=TwilioSmsBackend(
        account_sid="ACxxxx",
        auth_token="xxxx",
        from_number="+12025551234",
    ),
)

AWS SNS

from authwarden.sms.sns import AWSSNSSmsBackend

warden = AuthWarden(
    config=config,
    user_store=store,
    sms_backend=AWSSNSSmsBackend(region="us-east-1", sender_id="MyApp"),
)

AWS credentials resolve from the environment or instance profile — the standard boto3 credential chain, nothing authwarden-specific.

Writing your own backend

from authwarden.sms.base import SmsMessage

class MyProvider:
    async def send(self, message: SmsMessage) -> None:
        await my_sms_client.send(to=message.to, body=message.body)

warden = AuthWarden(config=config, user_store=store, sms_backend=MyProvider())

Enabling SMS for verification/reset

The backend alone isn't enough — also tell WardenConfig to actually use it as a channel:

config = WardenConfig(
    secret_key="...",
    verification_method="otp",               # SMS links don't make sense — OTP only
    verification_channels=["sms"],            # or ["email", "sms"] for both
    password_reset_method="otp",
    password_reset_channels=["sms"],
)

A user without a phone_number on file simply doesn't receive the SMS — NotificationService skips channels the user has no contact info for, rather than erroring.

Overriding SMS copy

from authwarden.sms.templates import SmsTemplates

class MySmsTemplates(SmsTemplates):
    def verify_otp(self, user, otp, expires_minutes):
        return f"[MyApp] Your code: {otp}. Valid {expires_minutes} min."

warden = AuthWarden(config=config, user_store=store, sms_templates=MySmsTemplates())