We frequently get asked by customers what exactly it means to unlock an iPhone. So I thought I would take this opportunity to impart some of my wisdom to our vast reading audience. Note that it normally doesn’t take long to impart my wisdom but in this case it may take a few paragraphs.

To understand what unlocking is all about, you need a little bit of background knowledge on cell phone technology. Here’s an article on the two different types of cell phone schemes used in the US. The basic thing you need to take away from that article is that any phone on the AT&T network can, theoretically, be used on the T-Mobile network and vice-versa (both use the GSM technology – think SIM card). This is in contrast to Sprint & Verizon where phones on one network cannot be used on the other (these are on the CDMA network – no SIM card).

So if you have a phone on Verizon, you can stop reading now – you can’t unlock your phone. It is forever bound to Verizon and if you want to switch carriers, you’ll have to get a new phone.

Now let’s say you’re on the AT&T network and you’ve got an iPhone (or a Blackberry, Samsung Galaxy, etc.). The phone’s hardware is perfectly capable of running not only on AT&T, but T-Mobile or just about any carrier in Europe (most of Europe is on the GSM standard). However, AT&T doesn’t want you to run their phone on anyone else’s network. They want all of your money for themselves. So what AT&T does, with Apple’s help, is install software on the phone that doesn’t allow the phone to run on any network except AT&T’s.

Does that make sense? Think of the iPhone as an ex-con on parole. He’d like to travel the world but he’s got this ankle bracelet on that prevents him from traveling. It’s not that he can’t travel – he’s perfectly able – it’s just that when he goes to get on an airplane, they’ll see his ankle bracelet and prevent him from boarding the plane. However, if he can get someone to come and take the bracelet off of him, well, then he’s free to travel as he’d like.

Okay, that’s not a perfect analogy, but I always like to work an ex-con into my posts if I can.

The point is, the iPhone being “locked” to AT&T’s network is a function of software, not hardware. If you can remove that software restriction – “unlock” the phone – you can then put a working SIM card from T-Mobile in the phone and it will work great. You’ll even get to keep your phone number. That’s right, if you have a phone number with T-Mobile, you unlock your iPhone, and then put your T-Mobile SIM card in the iPhone, your unlocked iPhone will ring whenever someone calls your number.

So that’s what unlocking is. Now the next questions are: Why would I want to do that? Why wouldn’t I want to do that? and How do I do that?

Why would I want to do that?

There are two main reasons to unlock an iPhone and run it on a different network. First, you might be able to save a lot of money. T-Mobile has significantly cheaper plans than AT&T so your monthly bill will be much less. Another reason is that some people don’t like AT&T’s coverage. If you’re on T-Mobile, you don’t have to worry about AT&T’s service.

Why wouldn’t I want to do that?

Unlocking your phone for another network is not all fun and games. There are five big drawbacks

1. T-Mobile does not support 3G service on an iPhone. You can still get your emails and surf the web, you’ll just have to do it over the Edge network.
2. No more visual voicemail. You’ll have to use the old method of calling your voicemail and then using the number pad to fast forward, skip, delete, etc. If you’ve never experienced visual voicemail, this isn’t a big deal. If you have, this is a huge minus.
3. Apple will not give you any support if they know your phone has been unlocked. They really hate it when people do this because it costs them money (they get a part of AT&T’s iPhone revenues), so they will tell you to get lost if you come in with an unlocked phone.
4. No more iPhone updates. Since Apple hates it when you unlock your iPhone, they remove the unlocking every time you update your phone. In addition, it usually takes a few weeks to months for hackers to figure out how to unlock the newest updates. This means your wonderful T-Mobile enabled iPhone just became useless. There are ways to downgrade to old versions of the iPhone software so not all is lost, but it’s a big hassle and something to be aware of.
5. Security problems. If you don’t take a few simple precautions after unlocking your phone, your iPhone can easily get hacked into. There’s an amusing story about a Dutch hacker that extorted people with unlocked iPhones and CNet has an article about how malicious software can be introduced to unlocked iPhones. These security problems can be prevented with some very simple precautions, but they are something to be aware of.

How do I do that?

The web is full of advice on how to unlock your iPhone but before I do that, let me state two things very clearly:

1. Jet City Devices does not do unlocking for customers and we are not at all suggesting that you unlock your phone. I’m writing this blog post because I get asked about it quite a bit and thought people would like to know more about it.
2. Unlocking your phone can cause all sorts of strange side-effects besides those listed above so be careful if you are going to proceed.

Alright, one more thing: Before you can unlock your iPhone, you have to first jailbreak it. Jailbreaking is a whole other topic of it’s own but it basically allows you to install your own software on the phone. So you jailbreak your phone and then install the unlocking software. That’s the gist of it.

I’m not going to detail for you how to unlock your phone because it really depends on what phone you have and what version of software you’re running. Also, tons of other people have already written about this. My suggestion if you want to do your own iPhone unlocking, start here:

http://blog.iphone-dev.org/

That is the main site for all things iPhone hacking related. A good place to look for the latest news. And for unlocking itself, I suggest this site:

http://www.redmondpie.com

Just do a search on their site for: iPhone [3g, 3gs, or 4] unlocking. You’ll find step-by-step instructions.

Lastly, if you don’t want to deal with all the hassle, just do a search on Craigslist for “iphone unlocking” in your city. You will definitely find someone that does it for about $25-$30. Just be careful – there’s a lot of scammers on Craigslist and you could end up with a stolen phone if you’re not careful.