javascript – Only on Firefox "Loading failed for the <script> with source"-ThrowExceptions

Exception or error:

I want to integrate Marketo form with my existing website on yii framework.
My code works on all the browsers except Firefox.

Excerpt from my code:

    $('#button').click(function () {
    var formData = {
        'Email': $('#UserInfo_email').val(),
        'FirstName': $('#UserInfo_first_name').val(),
        'LastName': $('#UserInfo_last_name').val(),
    MktoForms2.loadForm('//', mcId, formId, function (form) {
        var myForm = MktoForms2.allForms()[0];
        myForm.onSuccess(function (values, followUpUrl) {
            return false;

I get error on Firefox only with message

Loading failed for the <script> with source “”.

other browsers do the job correctly

note: munchkinId and formId are changed for posting here.

How to solve:

I just had the same issue on an application that is loading a script with a relative path.

It appeared the script was simply blocked by Adblock Plus.

Try to disable your ad/script blocker (Adblock, uBlock Origin, Privacy Badger…) or relocate the script such that it does not match your ad blocker’s rules.

If you don’t have such a plugin installed, try to reproduce the issue while running Firefox in safe mode.

  • If you cannot reproduce it in safe mode, it means your issue is linked to one of your plugins or settings.
  • Otherwise, it might be a different issue. Make sure you have the same error message as in the question. Also look at the network tab of the developer tools to check if your script is listed (reload the page first if needed).


I’ve just had the same issue – for me Privacy Badger on Firefox was the issue – not adblocker. Posting for posterity


I noticed that in Firefox this can happen when requests are aborted (switching page or quickly refreshing page), but it is hard to reproduce the error even if I try to.

Other possible reasons: cert related issues and this one talks about blockers (as other answers stated).


As suggested above, this could possibly be an issue with your browser extensions. Disable all of your extensions including Adblock, and then try again as the code is loading fine in my browser right now (Google Chrome – latest) so it’s probably an issue on your end. Also, have you tried a different browser like shudders IE if you have it? Adblock is known to conflict with domain names with track and market in them as a blanket rule. Try using private browsing mode or safe mode.


I ran into the same issue (exact error message) and after digging for a couple of hours, I found that the content header needs to be set to application/javascript instead of the application/json that I had. After changing that, it now works.


VPNs can sometimes cause this error as well, if they provide some type of auto-blocking. Disabling the VPN worked for my case.


I had the same problem (different web app though) with the error message and it turned out to be the MIME-Type for .js files was text/x-js instead of application/javascript due to a duplicate entry in mime.types on the server that was responsible for serving the js files. It seems that this is happening if the header X-Content-Type-Options: nosniff is set, which makes Firefox (and Chrome) block the content of the js files.


If the src is https and the certificate has expired — and even if you’ve made an exception — firefox will still display this error message, and you can see the exact reason why if you look at the request under the network tab.


Today I ran into the exact same problem while working on a progressive web app (PWA) page and deleting some cache and service worker data for that page from Firefox. The dev console reported that none of the 4 Javascript files on the page would load anymore. The problem persisted in Safe mode, so it was not an add-on issue. The same script files loaded fine from other web pages on the same website. No amount of clearing the Firefox cache or wiping web page data from Firefox would help, nor would rebooting the Windows 10 PC. Chrome all the time worked fine on the problem page. In the end I did a restore of the entire Firefox profile folder from a day-old backup, and the problem was immediately gone, so it was not a problem with my PWA app. Apparently something in Firefox got corrupted.


I had the same issue with firefox, when I searched for a solution I didn’t find anything, but then I tried to load the script from a cdn, it worked properly,
so I think you should try loading it from a cdn link, I mean if you are trying to load a script that you havn’t created.
because in my case, when tried to load a script that is mine, it worked and imported successfully, for now I don’t know why, but I think there is something in the scripts from network, so just try cdn, you won’t lose anything.

I wish it help you.


This could also be a simple syntax error. I had a syntax error which threw on FF but not Chrome as follows:

    <script src="">


I ran in the same situation and the script was correctly loading in safe mode. However, disabling all the Add-ons and other Firefox security features didn’t help. One thing I tried, and this was the solution in my case, was to temporary disable the cache from the developer window for this particular request. After I saw this was the cause, I wiped out the cache for that site and everything started word normally.

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