> For the complete documentation index, see [llms.txt](https://docs.satisfilabs.com/resource-center/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.satisfilabs.com/resource-center/marketing-engine/campaigns/messaging-campaigns/sms-regulations/sms-mms-regulations-for-usa.md).

# SMS/MMS Regulations for USA

SMS and MMS marketing in the U.S. is **strictly regulated** by the **CTIA**, and senders must comply to avoid penalties or message blocks.

### Key Restrictions (for long numbers only)

**Message Format**

* Standard SMS length: **160 characters** per message.
* Unicode messages are limited to **70 characters** per message.
* The **Euro (€) symbol, binary encoding, and concatenation** are not supported.

**Sender ID**

* Only **long numbers or short codes** can be used—**alphanumeric sender IDs are not allowed**.
* The sender's **FROM address** must use a **pre-approved U.S. sender number** in international format.

**Message Content**

* Messages must **not contain offensive, inflammatory, or harmful content**.
* If targeting minors, the content must be **appropriate for all ages**.
* **Excessive use of keywords and URLs** can trigger spam filters, leading to message blocks.

**Opt-in & Opt-out Requirements**

* **Opt-in consent is required** before sending any SMS/MMS marketing messages.
* Every marketing message **must include an opt-out option**.
* Senders must use **two-way numbers**, allowing recipients to unsubscribe at any time.

**Message Frequency & Volume Limits**

* **High-frequency senders** should purchase additional numbers.
* **Carriers may reject messages** if more than **one message per second** is sent from a single number.
* **Daily limit for long numbers**: **5,000 messages**—exceeding this may lead to number blocking.
* **For two-way SMS/MMS numbers**, carriers expect **balanced inbound and outbound traffic**.

Following these regulations ensures compliance and prevents disruptions in SMS marketing campaigns.