Why is AJAX returning HTTP status code 0?

Question

For some reason, while using AJAX (with my dashcode developed application) the browser just stops uploading and returns status codes of 0. Why does this happen?

score 113 · Answer 1 · edited Apr 27 '16 at 16:14

113

Another case:

It could be possible to get a status code of 0 if you have sent an AJAX call and a refresh of the browser was triggered before getting the AJAX response. The AJAX call will be cancelled and you will get this status.

edited Apr 27 '16 at 16:14

Dušan Maďar

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answered Sep 27 '12 at 12:56

mnk

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Thanks for pointing this out, it led me to realise that (as well as a browser refresh) a form submission can cancel the ajax call. – Magnus Smith Feb 27 '14 at 17:34
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Just do `
`
– Heitor Oct 07 '17 at 05:52
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@Heitor's suggestion worked for me -- my form's "submit" button was refreshing the page, meanwhile I had javascript trying to run an ajax call when the "submit" button was clicked. Result was that the ajax call was canceled – Nic Scozzaro Jun 25 '18 at 00:45
Hey, I missed a `e.preventDefault();` – SparK Apr 11 '19 at 16:03

score 104 · Answer 2 · edited Mar 22 '18 at 03:10

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In my experience, you'll see a status of 0 when:

doing cross-site scripting (where access is denied)
requesting a URL that is unreachable (typo, DNS issues, etc)
the request is otherwise intercepted (check your ad blocker)
as above, if the request is interrupted (browser navigates away from the page)

edited Mar 22 '18 at 03:10

Chris Burgess

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answered Jan 06 '10 at 20:43

Langdon

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I'm getting it when the connection is refused. For example, when debugging my site with Visual Studio, if I have stopped the debugging session, any request that tried to connect will get net::ERR_CONNECTION_REFUSED and the status code will be zero. That makes sense, since you can't have a status code if you can't connect to the server that's supposed to be providing one. – Triynko Dec 07 '15 at 20:12
I can confirm. I've got status==0 after shutting my web server down. – 9ilsdx 9rvj 0lo May 16 '17 at 12:19
i have errors because of 'cross-site scripting'; what should i do? – Oct 08 '17 at 10:12
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@nasimjahednia lookup CORS... the server you're trying to access needs to allow for cross site scripting from your domain. – Langdon Oct 11 '17 at 19:58
I'm confused. Is there no way to get the HTTP error code returned? This is a lot of different cases here (415, 404, etc?) – Edwin Evans Jul 26 '18 at 20:41
Is there a difference between cross site scripting for IOS mobile and Android/Windows on the other hand? Because I get status 0 only for mobile IOS... – user2718671 Sep 06 '18 at 13:26
@EdwinEvans there is no HTTP response code since there is never a response from the server in these cases. – Alex Mar 16 '21 at 16:43

Rafi · Answer 3 · 2014-07-08T18:37:34.397

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Same problem here when using <button onclick="">submit</button>. Then solved by using <input type="button" onclick="">

edited Jul 08 '14 at 18:37

answered Mar 12 '14 at 21:16

Rafi

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Bingo!! Anyone can explain why this? – Jorge Mar 01 '17 at 15:55
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By default HTML button type is 'submit', so clicking it will attempt submit form data. So it will execute the click action, then attempt to submit. If you use type 'button' it is no longer default type and will only perform onclick. – Christophe Roussy Jun 05 '17 at 11:12

score 7 · Answer 4 · answered Sep 03 '12 at 11:54

It is important to note, that ajax calls can fail even within a session which is defined by a cookie with a certain domain prefixed with www. When you then call your php script e.g. without the www. prefix in the url, the call will fail and viceversa, too.

score 7 · Answer 5 · answered Jun 23 '11 at 17:03

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Status code 0 means the requested url is not reachable. By changing http://something/something to https://something/something worked for me. IE throwns an error saying "permission denied" when the status code is 0, other browsers dont.

answered Jun 23 '11 at 17:03

Jagadeesh

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In this case, chrome currently will leave the request in a "Stalled" state until it times out. It can be caused by either a [Strict-Transport-Security](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Strict-Transport-Security) flag returned in a previous request from that server, or it can be a [Secure/HttpOnly](https://developer.mozilla.org/en-US/docs/Web/HTTP/Cookies#Secure_and_HttpOnly_cookies) flag on a cookie being sent with the request. – Shane Hughes Aug 30 '18 at 16:19

score 4 · Answer 6 · edited Aug 29 '18 at 09:23

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This article helped me. I was submitting form via AJAX and forgotten to use return false (after my ajax request) which led to classic form submission but strangely it was not completed.

edited Aug 29 '18 at 09:23

zb226

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answered Mar 12 '12 at 21:35

Martin Vseticka

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Dawn I hate the fact I was caught by this one again! `
` did the trick.
– Heitor Oct 07 '17 at 05:51

score 3 · Answer 7 · answered Apr 07 '12 at 21:51

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I found another case where jquery gives you status code 0 -- if for some reason XMLHttpRequest is not defined, you'll get this error.

Obviously this won't normally happen on the web, but a bug in a nightly firefox build caused this to crop up in an add-on I was writing. :)

answered Apr 07 '12 at 21:51

starwed

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You made a point, I had a problem with `jQuery.ajax()` XHR object. The request wasn't even created on AJAX call, still getting f.open is not a function and status code 0. Caused by: I was returning `$.ajaxSettings.xhr` object from `$.ajaxSetup({xhr})`, returning `new window.XMLHttpRequest();` instead solved the problem – klimpond Feb 16 '16 at 14:36

score 3 · Answer 8 · answered Mar 21 '14 at 14:01

I had the same problem, and it was related to XSS (cross site scripting) block by the browser. I managed to make it work using a server.

Take a look at: http://www.daniweb.com/web-development/javascript-dhtml-ajax/threads/282972/why-am-i-getting-xmlhttprequest.status0

score 3 · Answer 9 · answered Feb 08 '12 at 18:34

Because this shows up when you google ajax status 0 I wanted to leave some tip that just took me hours of wasted time... I was using ajax to call a PHP service which happened to be Phil's REST_Controller for Codeigniter (not sure if this has anything to do with it or not) and kept getting status 0, readystate 0 and it was driving me nuts. I was debugging it and noticed when I would echo and return instead of exit the message I'd get a success. Finally I turned debugging off and tried and it worked. Seems the xDebug debugger with PHP was somehow modifying the response. If your using a PHP debugger try turning it off to see if that helps.

score 2 · Answer 10 · answered Aug 08 '12 at 19:54

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"Accidental" form submission was exactly the problem I was having. I just removed the FORM tags altogether and that seems to fix the problem. Thank you, everybody!

answered Aug 08 '12 at 19:54

Insider Pro

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score 2 · Answer 11 · answered Dec 17 '13 at 17:07

We had similar problem - status code 0 on jquery ajax call - and it took us whole day to diagnose it. Since no one had mentioned this reason yet, I thought I'll share.

In our case the problem was HTTP server crash. Some bug in PHP was blowing Apache, so on client end it looked like this:

mirek@toccata:~$ telnet our.server.com 80
Trying 180.153.xxx.xxx...
Connected to our.server.com.
Escape character is '^]'.
GET /test.php HTTP/1.0
Host: our.server.com

Connection closed by foreign host.
mirek@toccata:~$

where test.php contained the crashing code. No data returned from the server (not even headers) => ajax call was aborted with status 0.

score 2 · Answer 12 · answered Dec 17 '14 at 22:56

In my case, it was caused by running my django server under http://127.0.0.1:8000/ but sending the ajax call to http://localhost:8000/. Even though you would expect them to map to the same address, they don't so make sure you're not sending your requests to localhost.

score 2 · Answer 13 · answered Apr 19 '18 at 14:40

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In our case, the page link was changed from https to http. Even though the users were logged in, they were prevented from loading with AJAX.

answered Apr 19 '18 at 14:40

Andy In NC

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interesting. I hope its my case. Since my iframe opens with https and on result success I send ajax to the http then I get status 0 – sonic Aug 05 '18 at 13:44

score 1 · Answer 14 · answered Jul 31 '14 at 08:15

For me, the problem was caused by the hosting company (Godaddy) treating POST operations which had substantial response data (anything more than tens of kilobytes) as some sort of security threat. If more than 6 of these occurred in one minute, the host refused to execute the PHP code that responded to the POST request during the next minute. I'm not entirely sure what the host did instead, but I did see, with tcpdump, a TCP reset packet coming as the response to a POST request from the browser. This caused the http status code returned in a jqXHR object to be 0.

Changing the operations from POST to GET fixed the problem. It's not clear why Godaddy impose this limit, but changing the code was easier than changing the host.

score 1 · Answer 15 · answered May 08 '17 at 02:18

I think I know what may cause this error.

In google chrome there is an in-built feature to prevent ddos attacks for google chrome extensions.

When ajax requests continuously return 500+ status errors, it starts to throttle the requests.

Hence it is possible to receive status 0 on following requests.

score 1 · Answer 16 · answered Jun 29 '17 at 00:55

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In an attempt to win the prize for most dumbest reason for the problem described.

Forgetting to call

xmlhttp.send(); //yes, you need this pivotal line!

Yes, I was still getting status returns of zero from the 'open' call.

answered Jun 29 '17 at 00:55

Gordon Rouse

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score 1 · Answer 17 · answered Dec 26 '18 at 18:49

In my case, I was getting this but only on Safari Mobile. The problem is that I was using the full URL (http://example.com/whatever.php) instead of the relative one (whatever.php). This doesn't make any sense though, it can't be a XSS issue because my site is hosted at http://example.com. I guess Safari looks at the http part and automatically flags it as an insecure request without inspecting the rest of the URL.

score 1 · Answer 18 · answered Apr 05 '19 at 17:07

In my troubleshooting, I found this AJAX xmlhttpRequest.status == 0 could mean the client call had NOT reached the server yet, but failed due to issue on the client side. If the response was from server, then the status must be either those 1xx/2xx/3xx/4xx/5xx HTTP Response code. Henceforth, the troubleshooting shall focus on the CLIENT issue, and could be internet network connection down or one of those described by @Langdon above.

score 1 · Answer 19 · answered Mar 11 '12 at 07:18

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In my case, setting url: '' in ajax settings would result in a status code 0 in ie8.. It seems ie just doesn't tolerate such a setting.

answered Mar 11 '12 at 07:18

blurrcat

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score 0 · Answer 20 · answered Sep 13 '18 at 06:14

Observe the browser Console while making the request, if you are seeing "The Same Origin Policy disallows reading the remote resource at http ajax..... reason: cors header ‘access-control-allow-origin’ missing" then you need to add "Access-Control-Allow-Origin" in response header. exa: in java you can set this like response.setHeader("Access-Control-Allow-Origin", "*") where response is HttpServletResponse.

score 0 · Answer 21 · answered Feb 09 '21 at 21:29

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In my case, I was making a Firefox Add-on and forgot to add the permission for the url/domain I was trying to ajax, hope this saves someone a lot of time.

answered Feb 09 '21 at 21:29

AEQ

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Why is AJAX returning HTTP status code 0?

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