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But phone numbers are not unique. They are regularly re-assigned to new customers.


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> Names are often not unique but phone numbers are.

Right out of "Myths programmers believe about phone numbers" which was on the HN front page a week back. Has everyone forgotten about landlines? Even cell numbers are not permanently assigned to a single person: especially in jurisdictions where pay-as-you-go accounts are the majority.


Phone numbers are not unique identifiers. In several regions around the world, phone numbers are reused. Please keep this in mind because it is very short sighted to say you will never expand globally.

Phone numbers are also recycled.

I have like 6 phone numbers listed in my phone contact list for my sister alone, because she changes numbers every time she job hops and gets a new work phone, so I really question how well phone numbers work either. Most of those numbers are no longer hers, but I've lost track of which ones.

I feel like there's a bubble of people for whom phone numbers are perhaps a useful, durable identity token, but I really think it's very much a bubble. Most people's phone numbers change fairly frequently.


Do they reuse the phone numbers after a while? Will I get phone calls for previous users of that same number?

Phone numbers are also recycled, probably much more often than email addresses.

I don't know enough about how it all works, but perhaps -- because the number isn't valid on its own -- giving the number to a different customer, with a different name, effectively invalidates its previous use and means it can be safely reused.

My experience is the same, 90% of unsolicited calls I get are from the same area code and prefix, only the last 4 digits are new.

I love how it makes it really easy for me to screen the calls however, as no-one I know has the same prefix and there are a couple area codes covering the local calling area.


According to the linked article, they have a list of public phone numbers. I guess they can cycle through fresh ones every few days.

Of course, if they simply provision a list of phone numbers and then give them up and get new ones, the new holders of the numbers won't be happy....


Phone numbers stored in an address book are not guaranteed to be unique(at least in the US) because they can be stored with or without area code and with or without country code.

I find they call from a new number every time.

Just like with email addresses, there are a nontrivial number of people who share the same phone number.

I think unique has a specific meaning in your context which isn't what the standard definition of unique means. There are never two people in a carrier's database assigned to the same number. It can however be assigned to another person as long as it is deassigned from the previous person. The number, at any point, is always unique.

In Australia it's outright common to have recycled numbers. I've had a few. My work phone had to be given a new number 3 times in the first 6 months until I had a useable one, because I kept getting random calls at all hours of the day/night looking for people who weren't me. It's mostly for work phones for some reason (I assume they have a higher rotation of useage as employees come and go, and nearly all companies use the same provider, Telstra), but my brother got a number that was someone else's before him too so it does happen privately.

The idea of phone numbers being the prime authenticator is laughable. I'll actively avoid any service who ever does this.


Gosh I hate when they want unique phone numbers.

I have a total of 6 LLCs(only 1 of them is profitable), and I use my same phone number for all of them.


You want to keep the same phone number, right?

Phone numbers do work that way.

That's always been the case. The problem is that, especially over the last couple of decades, people have built lots of systems with a central assumption being that phone numbers are uniquely tied to individuals.

So, instead of fixing those systems, I guess the idea is to adapt phone numbers to the faulty assumptions made about them.


The prior holder of that number was already a target. Numbers are reused quickly in area codes facing any possible future shortage.
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