Best Practices for SMS

SMS is an effective way to instantly reach people all over the world, but it comes with a wide range of rules and restrictions. Below we will discuss rules to bear in mind when getting set up to send SMS.

Opt-in & Opt-out

Make sure that your recipients agree to receiving messages from your company. If your customers did not opt-in to receive your SMS, this can be considered as spam. We recommend for an opt-in to be included in your Terms & Conditions, or even a separate tick box when people agree for you to store their contact details in your system.

Similarly, recipients should always to be able to tell you they do not want to receive your SMS anymore by opting-out. Some countries are stricter than others regarding this rule, and some operators may even have their own standards in this regard.

We recommend to include a Virtual Mobile Number or a (Sub-)Keyword with a shortcode in your message which allows people to opt in and out of your services. You can use MessageBird Numbers to automate an opt-in and opt-out flow on your account, learn more here: Automatic SMS Subscriptions (Opt-in/Opt-out)

SMS Character Limit

Be aware when sending SMS that there is a limited amount of characters per SMS. One SMS can contain up to 160 GSM characters, or 70 Unicode characters. If your SMS contains more than the maximum, two SMS will be sent out and you will be charged two SMS.

Please familiarise yourself with the information in this article, so you do not run into unexpected extra costs: Length of an SMS

Formatting your Numbers

All numbers should have a prefix for their respective country and be formatted as follows: 31612345678 . This means you should remove any + signs or 0’s at the start of the number, and make sure there is a country code at the start of your phone number. If the country code is not added, we cannot guarantee that the message will be sent to the right destination. For more info, check out this article: Numbers Format

Your Originator

When sending an SMS, you will be asked to provide an originator. This is the name or number from which the message is sent. When choosing an originator, there are some things you should keep in mind, as well as some restrictions as to how you can use the originator.

Read up more on choosing your originator here: Choosing an originator

Find out more about local restrictions here: Country Restrictions and Regulations.

Local Restrictions

Many countries have local restrictions in place when sending SMS. These restrictions are out of our control, as they are enforced by local operators. Restrictions are usually related to the originator or content of an SMS, for example you may not be allowed to send a URL in your SMS. We recommend checking the Country Restrictions and Regulations before sending to a destination, to make sure you don't run into any issues.


Note that you are billed for every SMS you send, rather than every SMS that is delivered. We will send every SMS that you submit to us to the operator, regardless of whether this is sent to an unreachable or an invalid number. For this we are charged by the operator, which is why we, in return, charge you. To avoid sending SMS to invalid or unreachable recipients, we recommend using our HLR API.

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