# What is a flash SMS?

> A flash SMS (class 0 message) is a text that appears immediately on the recipient's screen without being saved to the inbox by default, so it demands instant attention and disappears unless the user chooses to keep it. It is used for urgent, ephemeral alerts — critical security warnings, emergency notifications, or attention-grabbing prompts — where an ordinary inbox message might be missed or where you do not want the content stored.

- Canonical URL: https://www.broadnet.me/answers/what-is-flash-sms
- Language: en
- Last reviewed: 2026-07-22
- Publisher: BroadNet (https://www.broadnet.me)

## How it differs from normal SMS

A standard SMS lands in the inbox and stays there; a flash SMS (message class 0) pops up on the display immediately and is not stored unless saved. Both use the same network, just a different message-class flag. See /answers/what-is-a2p-sms.

## When to use it

Reach for flash SMS for genuinely urgent, time-critical, or sensitive alerts where immediacy matters and persistence is undesirable — emergency notices, fraud warnings, or one-off prompts. Overuse annoys recipients, so keep it rare.

## Support and limitations

Handset and network support for class 0 messages varies, so behaviour is not perfectly uniform across devices, and flash SMS is not a fit for anything the user may need to re-read later. Test on your target devices before relying on it.

## Alternatives

For urgent-but-persistent messages, a normal high-priority SMS on a direct route is usually the right choice; for rich urgent alerts on supported devices, consider RCS. See /answers/sms-for-payment-alerts and /answers/rcs-for-business.

## Related

- [All answers](https://www.broadnet.me/answers)
- [Glossary](https://www.broadnet.me/answers)
- [What is a silent SMS?](https://www.broadnet.me/answers/what-is-silent-sms)
- [What is A2P SMS?](https://www.broadnet.me/answers/what-is-a2p-sms)
- [How do you use SMS for payment and transaction alerts?](https://www.broadnet.me/answers/sms-for-payment-alerts)
- [What is RCS for business (RBM)?](https://www.broadnet.me/answers/rcs-for-business)
- [What is a concatenated SMS?](https://www.broadnet.me/answers/what-is-concatenated-sms)
- [A2P SMS](https://www.broadnet.me/products/a2p-sms)