Why does Twilio show 'delivered' but the OTP never arrives?

'Delivered' in Twilio means the carrier accepted the message handoff — not that it reached the device. The carrier can still filter it after that point. Check your A2P campaign use case registration and test across multiple carriers to identify which one is dropping it.

How do I register my Twilio number for OTP sending?

In Twilio Console, go to Messaging > Services > Compliance. Register your brand, then create a campaign with the 'Two-Factor Authentication' use case. Attach your sending number to that campaign. Approval typically takes 24–72 hours.

What's the fastest fix if OTPs are blocked right now?

Switch to a toll-free number (1-8XX) registered for OTP use. Toll-free numbers have a separate registration track, faster approval, and higher throughput than 10DLC long codes. This is the fastest path to reliable OTP delivery while fixing your long code registration.

Twilio · Problem Fix

Twilio OTP Code Not Arriving

Quick answer: Open Twilio Console > Verify Logs, click the failed attempt timestamp, and read the delivery status and error code before changing content or numbers. Twilio describes Verify SMS as best-effort and points developers to Verify Logs for delivery status, per Twilio Help Center, Sept 2026.

1. A2P 10DLC campaign not registered for OTP use case

Carriers require the campaign use case to match message content. If your campaign is registered as 'marketing' and you're sending OTP codes, it can be silently filtered. Re-register with the 'Two-Factor Authentication' or 'Account Notifications' use case.

2. Message content triggering spam filters

Short numeric-only messages with words like 'code', 'verify', or 'security' can trigger carrier heuristics. Add context: 'Your SideGuy verification code is: 482910. This code expires in 10 minutes.' Content with clear sender context passes more reliably.

3. Rate limiting on 10DLC long codes

10-digit long codes are capped at 1 message per second. If users trigger OTP requests in quick succession (double-tap, retry), messages queue and may time out before delivery. Use a messaging service pool or toll-free number for higher throughput.

4. Recipient's carrier blocking the sending number

Individual carriers maintain number-level blocklists. If your number has a poor sending history, specific carriers may block it without notification. Test the same code send to numbers on AT&T, Verizon, and T-Mobile separately to isolate the carrier.

5. International delivery rules

OTP delivery outside the US has separate carrier agreements. Many countries require local number registration or use of in-country numbers. Check Twilio's country-specific compliance requirements if your users are international.

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