Don’t reply to those SMS. Your geolocation can be derived from your reply, even a STOP or UNSUBSCRIBE reply.

Can you explain how this works if you don't click any links?

I read about it on HN some months ago. I don’t recall if it was in comments or an article. But I read the info and sources and was convinced enough at the time. I’m sorry I didn’t save the original info. I’ll try some googling “geolocation from SMS” and see what I can find.

Here’s the best I could find:

https://stackoverflow.com/questions/18523417/can-i-retrieve-...

(Twilio is awesome by the way)

That information is completely derived from the phone number.

Presumably if they have the number to text to, they already roughly know the geolocation for most people, through the area code.

That’s not what I’m talking about. And since number portability and mobile devices became possible, area codes are mostly irrelevant. For example, I’ve lived 2000 miles from the area code of my phone number for probably 10 years now.

They're not mostly irrelevant. 72% of Americans live in or close to the city that they grew up in. Area code is remarkably accurate.

Only in the US (or whole NANP?)

Mobile numbers are non-geographic everywhere else that I know of.

Well, depends. For example, Singapore's numbers are 'non-geographic' in that sense. But Singapore itself is small enough.

Greek here, mobile phones are non-geographic but used to be service provider specific, but even this practice isn't applicable due to number portability.

Landlines used to be geographic but this isn't relevant any more again new to number portability.

I mean non-geographic within the country. As far as I know, the US practice of assigning mobile numbers to 'area codes' is unique.

Yes. I was broadly agreeing with you.

Just saying that some countries are small enough that it's essentially the same.

Can you provide a pointer showing how this is supposed to work?

Yes, would like to learn more as well.

I read about it on HN some months ago. I don’t recall if it was in comments or an article. But I read the info and sources and was convinced enough at the time. I’m sorry I didn’t save the original info. I’ll try some googling “geolocation from SMS” and see what I can find.