---
title: "Flash SMS"
description: "A flash SMS is a Class 0 text message that the phone displays immediately on screen without storing it in the inbox by default. It is defined by the message class in the data coding scheme."
canonical: "https://omnichannels.ai/glossary/flash-sms/"
language: "en"
updated: "2026-10-10"
publisher: "BroadNet Technologies"
brand: "OmniChannels.ai"
---

# Flash SMS

Canonical: https://omnichannels.ai/glossary/flash-sms/
Language: en
Publisher: OmniChannels.ai by BroadNet Technologies

**Definition:** A flash SMS is a Class 0 text message that the phone displays immediately on screen without storing it in the inbox by default. It is defined by the message class in the data coding scheme.

3GPP TS 23.040 says that when a mobile-terminated message is class 0 and the phone can display short messages, it shall display the message immediately. The class is set in the TP-Data-Coding-Scheme (3GPP TS 23.038).

Flash SMS is used for urgent alerts or messages that should not be kept on the device. Some users find them intrusive, and the user may be able to save them manually.

Support is uneven: some handsets, operators and routes ignore the class or convert it to a normal SMS, and some firewalls treat flash messages as suspicious.

Do not rely on flash SMS for security. A recipient can still read, photograph or save the message, so OTPs should be protected by short validity instead.

## Sources

- [3GPP TS 23.040 — Technical realization of the Short Message Service (SMS)](https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=747)
- [3GPP TS 23.038 — Alphabets and language-specific information](https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=745)