How did you get my IP address?

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Summary: Your IP address is the fundamental way of identifying your computer on the internet. Your IP address is available to any service you connect to.

I'm constantly amazed at how many people are concerned about the privacy of their IP address.

I guess I shouldn't be that amazed, because of the number of other questions I get by people trying to trace an IP address to a specific person or location.

Folks, there is no privacy with respect to your IP address. But that does not mean just anyone can actually find you.

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When you connect to any web site, your IP address given to that site so that it knows where to send the data back. It's that simple. If your IP address wasn't included, the web server wouldn't know how to get you the web pages you want to look at.

That also means that web servers that 'do something' - like process a form or take a question, have access to that information. When you post a question on my ask a question page, the software that processes your question knows your IP address, and includes that information on the automated email that confirms your question.

The only difference between what my form does and the rest of the internet is that my form shows you what I know. Every website you visit also knows your IP address and can do whatever they like with it.

But "what they can do with it" is very, very little.

Most people are afraid that they can somehow be physically located by their IP address. Yes, it is technologically possible, but it requires that your ISP provide the information. The only time they do is under court order or other legal pressure. Unless you expect the police to come after you for some reason, no one will find your physical location from your IP address.

In fact, all I could tell from the original questioner is that they were using an ISP based in England, and that they are possibly located in a specific region in England. To learn more I'd have to get their ISP to tell me - which they won't.

Now, I still won't publish the IP address here - or anywhere for that matter. With an IP address, it is possible to attack the computer across the internet without knowing it's location. For example one could stage a denial of service attack - attempting to overwhelm the computer at that IP address with bogus data.

But you still won't know where that computer is.

Now, as to email sometimes your email provider will include the email address of your computer, particularly if you use POP3/SMTP to connect to get your mail. For web based mail services like HotMail, GMail and the like results are mixed. Some will and some won't include your IP address in the header. In fact I've even seen HotMail be very inconsistent about this - sometimes it does, sometimes it does not.

But as I keep telling people, in the long run it doesn't matter.

In fact, come to think of it, everyone who's ever gotten an email from me has my IP address in the mail headers.

It just the way things work.

Related:

• Ask Leo! - What can people tell from my IP address?

• Ask Leo! - Can I get someone's name and address from their IP address?

• Ask Leo! - Getting all worked up over IP tracing