Get hostname of current request in node.js Express

Question

So, I may be missing something simple here, but I can't seem to find a way to get the hostname that a request object I'm sending a response to was requested from.

Is it possible to figure out what hostname the user is currently visiting from node.js?

It's in the request headers. Well I thought so but now I don't see it ... hmmmm — jcolebrand, Sep 21 '11 at 21:53
Thought so ... just wasn't pulling it out of the ole noggin. Glad you got it! — jcolebrand, Sep 22 '11 at 02:05
@Jesse Hey, that is actually not correct. request.headers.host isn't the hostname of the server based on the OS, it's the host header name sent along with the HTTP request. If your server responds to any HTTP request regardless of the host header then that value could be ANYTHING that the client decides to send. — Rob Evans, May 30 '13 at 12:50
@RobEvans - If you read the last line of the question, that's exactly what I was looking for. A client sending a fake hostname header is a bizarre use case that I wouldn't personally worry about trying to support. — Jesse, Jul 19 '13 at 20:13
Possible duplicate of [How to check the HOST using ExpressJS?](https://stackoverflow.com/questions/6503331/how-to-check-the-host-using-expressjs) — niry, Jan 23 '18 at 22:57
@niry Definitely not a dupe, the question you linked is trying to check a subdomain, and both the question and answers are far lower quality than this one. How do I get rid of this annoying dupe banner? — Jesse, Jan 24 '18 at 21:08
@jesse, the subdomain isn't even mentioned there and the answers are exactly the same, "req.headers.host" and even better "req.hostname". Duplication isn't about "quality" or votes: "This question has been asked before and already has an answer." Speaking about quality, it is not clear from your question if you want the "hostname" or the Host header of the request, and therefore, the answer to the former, got much higher votes (2x) than the one you selected. Since you indicated that the question is about the Host header (mistakenly calling it "hostname header"), your question is duplicate. — niry, Jan 25 '18 at 21:42
I would consider this thread the canonical SO thread on this specific subject. In the interest of continuing to help the many people who found both answers below helpful, I will not personally be closing this question as a dupe. Moderators are welcome to do whatever they like. — Jesse, Jan 26 '18 at 20:50

stephenbez · Answer 1 · 2014-02-19T18:19:31.060

291

You can use the os Module:

var os = require("os");
os.hostname();

See http://nodejs.org/docs/latest/api/os.html#os_os_hostname

Caveats:

if you can work with the IP address -- Machines may have several Network Cards and unless you specify it node will listen on all of them, so you don't know on which NIC the request came in, before it comes in.
Hostname is a DNS matter -- Don't forget that several DNS aliases can point to the same machine.

edited Feb 19 '14 at 18:19

answered Feb 22 '12 at 17:20

stephenbez

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Although this will work to get the machine's hostname, I can have a machine set up to answer to multiple hosts, so this wouldn't be accurate. – Jesse Feb 22 '12 at 18:07
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However this one is better - because you can use it in modules that do not run always inside context of HTTP app – Radagast the Brown Nov 21 '12 at 11:41
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And importantly this one answers the question as it was written. I think the question is actually wrong if this is not the answer. – Rob Evans May 30 '13 at 13:02
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This correlates with the `hostname` command which *should* be a valid DNS name but is not required to be. For example, under OS X you'll get names like `my-machine.local` which is not resolvable with DNS. To figure out the external IP of the machine you'll need to hit a [service that performs this function](http://ipchicken.com/) or use the [STUN protocol](http://en.wikipedia.org/wiki/STUN) to figure it out. – tadman Jun 05 '13 at 14:35
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This is *always* accurate. It returns the machine's hostname, which is what the title of the question asked. (The text of this one asked a different question). The hostname used on an incoming HTTP request is a different matter. – Cheeso Aug 31 '13 at 17:40
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I'd be careful with this if you are using AWS servers where their server name changes after reboot. – Taku Mar 16 '15 at 16:58
@RobEvans Questions can't be "wrong". Answers, however, can be. As this one is, since it doesn't answer the question. – B T Mar 23 '15 at 07:33
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@BT For "wrong" read explained poorly, misleading, prone to interpretation. Keep in mind that the original question was different to the one currently shown. It was edited later. This answer was correct given the question at the time, which has since changed. – Rob Evans Mar 23 '15 at 12:43
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I see. I'd still use "misleading" rather than wrong. Cause saying wrong just makes it sound like you just wanted a different answer to be asked, which made you seem a bit self centered. But I understand you now : ) – B T Mar 23 '15 at 21:06
Internal hostname might not match the DNS hostname and might be not be accessible by the client. – arboreal84 Jul 27 '16 at 20:19
I downvoted this answer because `os.hostname` - as the name implies and the docs state - `returns the hostname of the operating system`. Depending on the runtime environment, this may be - and likely is - different from the requester’s `host` used in the HTTP request. The latter is available via `req.getHeader('host')` in node.js v7.70, or `req.headers.host` in v0.1.5 – AndreasPizsa Sep 20 '18 at 12:16

score 262 · Accepted Answer · edited Oct 23 '14 at 13:57

262

If you're talking about an HTTP request, you can find the request host in:

request.headers.host

But that relies on an incoming request.

More at http://nodejs.org/docs/v0.4.12/api/http.html#http.ServerRequest

If you're looking for machine/native information, try the process object.

edited Oct 23 '14 at 13:57

Paul D. Waite

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answered Sep 21 '11 at 22:31

cjohn

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Ah, awesome - FWIW, there would be no way to detect the actual host without a request, you could have multiple hosts configured, but this is what I was looking for! – Jesse Sep 22 '11 at 00:38
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Did the trick, thanks! In Express 4, I had to do this update: **req.headers.host** – Gene Bo Jun 24 '15 at 03:07
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Wrong! `request.headers.host` returns `http://127.0.0.1` but not a production server domain name – Green Jun 28 '16 at 22:11
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`req.headers.host` is provided by the user. I can craft a request in 1 line of python and send you a request without that field making your code crash – arboreal84 Jul 28 '16 at 18:31
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request.headers.host is now deprecated, instead you can use request.headers.hostname – Syam Danda Dec 08 '16 at 09:45
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`req.hostname` does not include the port, which `req.headers.host` does include the port. – Dustin Graham Mar 19 '19 at 23:15
But `req.hostname` is specific to Express, right? The original answer was about a generic NodeJS application. – ivosh May 17 '19 at 22:40
@arboreal84 as you can see in [Express docs](http://expressjs.com/en/api.html#req.hostname) req.hostname is derived from host header, so there shouldn't be any problem using req.headers.host. Checking if it is not undefined is the solution. – therealak12 Dec 15 '20 at 18:08
Deprecated use req.hostname – Rami Jamleh May 16 '22 at 06:09

score 46 · Answer 3 · answered Feb 08 '18 at 03:41

46

Here's an alternate

req.hostname

Read about it in the Express Docs.

answered Feb 08 '18 at 03:41

Eddie

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This is the correct answer, as req.headers.host gives host:port – ekerner Feb 12 '19 at 12:38
what's the different between req.hostname and req.host – RayLoveless Aug 20 '19 at 16:37
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req.host is deprecated. If you use that, express will output a warning says 'deprecated req.host: Use req.hostname instead' – bruceczk Jan 13 '20 at 02:51

score 9 · Answer 4 · answered Oct 05 '14 at 06:37

9

If you need a fully qualified domain name and have no HTTP request, on Linux, you could use:

var child_process = require("child_process");

child_process.exec("hostname -f", function(err, stdout, stderr) {
  var hostname = stdout.trim();
});

answered Oct 05 '14 at 06:37

dricket

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BTW there's also `hostname` command in Windows (but you invoke it without parameters) – jakub.g Nov 28 '16 at 12:37
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@jakub.g Yes, _BUT_, it doesn't return the _fully-qualifed_ host name. – fourpastmidnight May 28 '21 at 02:46

arboreal84 · Answer 5 · 2016-07-27T20:35:25.130

First of all, before providing an answer I would like to be upfront about the fact that by trusting headers you are opening the door to security vulnerabilities such as phishing. So for redirection purposes, don't use values from headers without first validating the URL is authorized.

Then, your operating system hostname might not necessarily match the DNS one. In fact, one IP might have more than one DNS name. So for HTTP purposes there is no guarantee that the hostname assigned to your machine in your operating system configuration is useable.

The best choice I can think of is to obtain your HTTP listener public IP and resolve its name via DNS. See the dns.reverse method for more info. But then, again, note that an IP might have multiple names associated with it.

Zee · Answer 6 · 2023-02-16T14:10:13.693

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You can simply use below code to get the host.

request.headers.host

edited Feb 16 '23 at 14:10

answered Dec 07 '21 at 07:41

Zee

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Mahabub Sunny · Answer 7 · 2022-05-29T20:17:45.523

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I think what you want is to identify cross-origin requests, you would instead use the Origin header.

const origin = req.get('origin');

Use this you can get a request Client-Side URL

edited May 29 '22 at 20:17

answered May 29 '22 at 20:16

Mahabub Sunny

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score 0 · Answer 8 · answered May 06 '23 at 08:05

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You can get the client side url from the headers of the request, which has a property origin. So:

request.headers.origin

answered May 06 '23 at 08:05

kob003

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Get hostname of current request in node.js Express

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