> ## Documentation Index > Fetch the complete documentation index at: https://kero.chat/help/llms.txt > Use this file to discover all available pages before exploring further. # What is SMS? > Learn how SMS messaging works in Kero, including Sender IDs, message length, delivery, consent and fallback. SMS (Short Message Service) is one of the most widely supported mobile messaging channels, allowing businesses to send text messages directly to customers' mobile phones. With Kero, you can use SMS to send notifications, alerts, reminders, verification messages and other business communications, either as a standalone messaging channel or alongside RCS and WhatsApp. SMS does not require the recipient to install a separate messaging app or have a mobile data connection, making it a useful channel for reaching customers across a wide range of devices and mobile networks. ## How SMS works An SMS message is sent from your business through Kero to the recipient's mobile network for delivery to their mobile phone. The recipient generally sees the message in their phone's standard messaging application. Depending on the destination country and mobile network, your message may appear as coming from: * Your business or brand name * A dedicated mobile number * Another number allocated for business messaging The name or number displayed to the recipient is known as the **Sender ID**. > [!NOTE] > > **Sender ID requirements vary by country.** > > Some countries allow businesses to use an alphanumeric Sender ID without registration, while others require registration or approval before messages can be delivered. > > Check the **SMS Sender ID requirements by country** guide in Messaging Resources before sending to a new destination. ## What can you use SMS for? SMS is suitable for many types of business communication, including: * Order and delivery notifications * Appointment reminders * Service alerts * Account notifications * One-time passwords (OTPs) and verification codes * Customer updates * Promotional messages, where appropriate consent has been obtained Because SMS is supported on virtually all mobile phones, it is also useful when a richer messaging channel is unavailable. ## SMS message length SMS messages have character limits that depend on the characters used. A message using the standard GSM character set can contain up to **160 characters** in a single SMS. Longer messages are divided into multiple SMS parts. Most modern mobile devices reassemble these parts so that the recipient sees one continuous message. Messages containing characters outside the standard GSM character set, including many non-Latin characters and emojis, may require **Unicode** encoding, which has different character limits. The number of SMS parts used can affect the cost of your message. > [!TIP] > > **Keep an eye on your message length.** > > Kero helps you see the length and number of SMS parts while composing your message, so you can understand how your content affects message usage before sending. For the exact character limits, multipart SMS rules and Unicode examples, see [SMS message length & character limits](https://kero.chat/help/product/channels/sms/sms-message-length-character-limits.md). ## SMS delivery When you send an SMS through Kero, the message is submitted to the relevant messaging network for delivery. Where delivery reports are available, Kero uses the information returned by its messaging providers to display the message status. An SMS may not be delivered for several reasons, including: * An invalid or inactive mobile number * The recipient's device being unavailable * Network restrictions or temporary network issues * Sender ID restrictions * Destination-country messaging rules > [!NOTE] > > **Submitted does not always mean delivered.** > > A message may be accepted for processing without confirmation that it has reached the recipient's device. Delivery status depends on the information available from the messaging provider and mobile network. ## SMS and customer consent Businesses are responsible for ensuring that they have the appropriate permission or other lawful basis to send messages to their customers. Consent and opt-out requirements vary depending on the type of message and the country in which the recipient is located. For promotional messaging in particular, ensure that customers have provided the appropriate consent and have a clear way to opt out of future communications. You should also maintain accurate consent records and honour applicable opt-out requests. ## SMS alongside RCS and WhatsApp SMS can be used on its own, but it also plays an important role in an omnichannel messaging strategy. RCS and WhatsApp can provide richer experiences, including images, buttons and interactive content. SMS provides broad mobile reach and can be used as an alternative when another messaging channel is unavailable. This makes SMS particularly useful as a **fallback channel**. For example: **RCS → SMS** When an RCS message cannot be sent or delivered under certain conditions, Kero may attempt to send an SMS instead, provided fallback has been configured and the applicable routing conditions are met. > [!NOTE] > > **SMS fallback is not automatic for every failed message.** > > Fallback must be configured for the relevant messaging journey, and it is attempted only when the applicable routing and failure conditions are met. > > Sending an SMS as fallback does not guarantee delivery. ## Getting started with SMS To start sending SMS with Kero: 1. **Check Sender ID requirements.** Confirm whether your destination country requires registration or approval. 2. **Set up your SMS Agent.** Configure the SMS sending identity you will use in Kero. 3. **Prepare your recipients.** Add or import the contacts you want to message and ensure you have the appropriate permission to contact them. 4. **Create your message.** Write your SMS and review its character count and number of message parts. 5. **Send your message.** Send an individual message or use SMS as part of a campaign. For detailed instructions, see [Set up your SMS Agent](https://kero.chat/help/product/channels/sms/setup-your-sms-agent.md) and [Send an SMS message](https://kero.chat/help/product/channels/sms/send-an-sms-message.md). This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.