About SMS and MMS

SMS and MMS are two protocols used by mobile devices to send text messages. Activity Messenger supports both yet tries to make it completely transparent to you.


# Short Message Service (SMS)

SMS or Short Message Service is the protocol used by mobile devices to transmit text messages. It dates back to the 1990s. SMS are limited in the number of characters. For English and French alphabets, that is 160 characters.

Activity Messenger further limits to 135 characters in order to allow for a shortened URL to be appended to the message. If the message you write is longer, it will be truncated. Messages are not truncated in emails though. There is no limit on email character length.


# Multimedia Message Service (MMS)

MMS or Multimedia Message Service is an extension of the SMS protocol which allows attaching media files like images. File size is limited by carriers. In North America, experimentation shows that 500 Kb or half a megabyte is the limit to be safe.

All devices support MMS however a data plan is required to be able to receive MMS. Carriers will not deliver media files to mobile devices that do not have data plans.

When you attach attach an image or video to the text message you build, Activity Messenger will automatically send an MMS instead of an SMS. This process is fully transparent.

When you attach a YouTube or Vimeo video to a text message, Activity Messenger will include a thumbnail image of the video. That image is safely below the 500 Kb limit. You can be asured carriers will deliver it.


# Should I attach images?

Considering you may have some participants that do not have data plans, you may question whether it makes sense to attach images or not. We recommend you do for these reasons:

  • Your message will have more impact and invite the participant to read it and even click on the link you sent. A picture is worth a thousand words.
  • You can also send by email. Participants without data plans will receive the email with the image. They won't miss out.
  • Participants can choose their notification perference. Over time, they will decide on their favorite medium to be contacted by you. Consult the Managing notifications page to learn more.

# Twilio

Activity Messenger uses Twilio as the third-party service to send and receive both SMS and MMS. Twilio interfaces with carriers across North America to ensure delivery of text messages. Having been around for a long time, Twilio provides a very reliable service.


# Pricing

Unlike email, sending SMS is not free. Activity Messenger pays Twilio for every SMS and MMS you send. In turn Twilio pays carriers for every SMS/MMS they deliver.

In addition MMS are more expensive than SMS. Nevertheless, Activity Messenger charges you the same regardless of the text message protocol. We do not want you to feel constrained when writing the perfect message to send to your participants. Consult the Pricing page for Activity Messenger pricing information.




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