---
title: "What are trigger error codes in Multi-Channel Fallback?"
description: "Trigger error codes let you control *when* the platform moves to the next channel. By default, **any** failure on a channel (except the last) can trigger the next step. You can narrow this to specific delivery error codes only. ## Default behaviour (empty selection)…"
url: "https://www.smsgatewaycenter.com/blog/kb/what-are-trigger-error-codes-in-multi-channel-fallback/"
updated: "2026-06-29"
category: "Users / Multi-Channel Fallback"
---

# What are trigger error codes in Multi-Channel Fallback?

Trigger error codes let you control *when* the platform moves to the next channel. By default, **any** failure on a channel (except the last) can trigger the next step. You can narrow this to specific delivery error codes only.

## Default behaviour (empty selection)

If you leave trigger codes empty for a channel, failover to the next channel happens on **any** delivery failure for that step. This gives maximum retry coverage—recommended for OTP and critical alerts.

## Specific error codes

For SMS or WhatsApp steps (not the last channel), open the error-code dropdown and select one or more codes. Failover then happens **only** when one of those codes is returned.

## Example use cases

- **Empty triggers:** Any undelivered SMS should try WhatsApp.
- **DND / NCPR only:** Failover only when the number is on DND—not for invalid numbers.
- **Specific gateway errors:** Retry only on timeout or temporary failures.

## Last channel in sequence

The final step has nowhere to fall back to, so trigger error codes are not configured for it.

### More Related Articles

- [How do I preview fallback messages before going live?](https://www.smsgatewaycenter.com/blog/kb/how-do-i-preview-fallback-messages-before-going-live/)
- [Can I use Fallback for promotional bulk campaigns?](https://www.smsgatewaycenter.com/blog/kb/can-i-use-fallback-for-promotional-bulk-campaigns/)
- [Why is my fallback flow not trying the next channel?](https://www.smsgatewaycenter.com/blog/kb/why-is-my-fallback-flow-not-trying-the-next-channel/)

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