eli5: Why does the text alert system need to know my mobile carrier?


Putting a book on hold from my library, and one of the options is to get a text message when it is ready for pickup.

The online form requires me to specify my mobile carrier.

Why is this necessary? It’s not like I need to know if someone is on Verizon or T-Mobile or whatever to send them a text… is this an artifact of a time when this WAS necessary? Or am I missing something?

In: 3

There’s a slightly obscure method of being able to send text messages via email, sorta. If you know a person’s carrier and phone number you can email them a SMS text. This can avoid fees and issues with sending texts from online sources which generally has a cost per text. Its a janky work around, but it works

In even older days, places may buy bulk texting plans from carriers to on-carrier numbers, so knowing your carrier they could make sure to send it via the right plan for them so that its cheapest. There was a time where if you sent texts on the same carrier, costs were basically zero, but if it was to another carrier, it may cost a tiny amount

Forms like that often ask semi-relevant information for market research. Most people don’t even think about it and just write down their carrier, giving the business an extra bit of info. That info could in theory be sold (sounds dull, but people pay for all sorts of information).

They may be using an email-to-mms gateway, in which case they need to know the email address associated with your phone number, which can be determined knowing the carrier.

Thanks all. The email-to-SMS explanation makes perfect sense here.