# What is rate limiting in SMS?

> Rate limiting caps how many messages or requests are accepted in a given time window — per API key, per sender, or per destination number — to protect throughput, enforce fair use, and defend against abuse such as SMS pumping. It is expressed as a rate (for example messages per second) and is what keeps one runaway job or one attacker from degrading delivery for everyone.

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

## Why it exists

Operators and platforms allocate finite throughput, so a provider meters submission to stay within route capacity and honour fair-use terms. Rate limiting also blunts SMS pumping, where fraudsters trigger floods of OTPs to earn a cut of the traffic. See /answers/what-is-sms-pumping and /answers/what-is-tps.

## Where limits apply

Common dimensions are per API key (your account's overall submission rate), per sender ID or number, and per destination MSISDN (to stop repeated sends to one victim). Verification flows should cap OTP requests per number and per IP. See /answers/sms-otp-best-practices.

## How to work with it

Design senders to respect HTTP 429 / SMPP throttling responses with exponential backoff, batch large campaigns within your allotted rate, and request a higher limit ahead of a known spike rather than hitting the ceiling live. See /answers/what-is-throughput-sla.

## Rate limiting vs throttling

The terms overlap: rate limiting usually means a hard cap you must stay under, while throttling means the platform is actively slowing your traffic to a sustainable rate. Both protect delivery. See /answers/what-is-cps.

## Related

- [All answers](https://www.broadnet.me/answers)
- [Glossary](https://www.broadnet.me/answers)
- [What is TPS (Transactions Per Second)?](https://www.broadnet.me/answers/what-is-tps)
- [What is a message queue in messaging?](https://www.broadnet.me/answers/what-is-a-message-queue)
- [What is CPS (Calls Per Second)?](https://www.broadnet.me/answers/what-is-cps)
- [What is a throughput SLA?](https://www.broadnet.me/answers/what-is-throughput-sla)
- [What is SMS pumping / artificial inflated traffic (AIT)?](https://www.broadnet.me/answers/what-is-sms-pumping)
- [What are SMS OTP best practices?](https://www.broadnet.me/answers/sms-otp-best-practices)
- [SMS API](https://www.broadnet.me/products/sms-api)
- [Developer docs](https://www.broadnet.me/developers)