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Firefox can't load websites but other browsers can

This article describes problems where Firefox cannot load websites, but other web browsers (such as Internet ExplorerSafariEpiphany on Gnome or Konqueror on KDE) can. When this happens, Firefox may show a Server not found or Unable to connect error message.

Internet Security software blocking Firefox

If you were able to load websites until you updated Firefox or until your Internet security software was updated, reconfigured or a new one was added, your Internet security software (including firewalls, antivirus programs, anti-spyware programs, and more) is likely preventing Firefox from connecting to the Internet.

Note: Some Internet security programs can block Internet access even when they are in a "disabled" state.

In general, you should make sure your Internet security software is up-to-date and remove Firefox from your program's list of trusted or recognized programs, then add it back. For instructions on how to configure some programs, see the Configure firewalls so that Firefox can access the Internet article.

Firefox connection settings

If you connect to the Internet through a proxy server that is having connection problems, you will not be able to load websites. To check your Firefox proxy settings:

  1. Click the menu button New Fx Menu and choose Options.Preferences.
  2. Select the Advanced panel.
  3. Select the Network tab.
  4. In the Connection section, click Settings….
  5. Change your proxy settings:
  6. Close the Connection Settings window.
  7. Close the about:preferences page. Any changes you've made will automatically be saved.

If you find that changes you make to your Firefox connection settings are not remembered when you restart Firefox, see How to fix preferences that won't save.

IPv6

Firefox supports IPv6 by default, which may cause connection problems on certain systems. To disable IPv6 in Firefox:

  1. In the address bar, type about:config and press EnterReturn.

    • The about:config "This might void your warranty!" warning page may appear. Click I'll be careful, I promise!I accept the risk! to continue to the about:config page.
  2. In the FilterSearch field, type network.dns.disableIPv6.
  3. In the list of preferences, double-click network.dns.disableIPv6 to set its value to true.

DNS Prefetching

Firefox attempts to speed up loading new websites by using DNS Prefetching, which can cause page load errors with some system configurations. To disable DNS Prefetching:

  1. In the address bar, type about:config and press EnterReturn.

    • The about:config "This might void your warranty!" warning page may appear. Click I'll be careful, I promise!I accept the risk! to continue to the about:config page.
  2. Right-clickHold down the Ctrl key while you click in the list of preferences, select New, and then select Boolean.
  3. In the Enter the preference name window, enter network.dns.disablePrefetch and click OK.
  4. Select true when prompted to set the value and click OK.

Firefox cannot load certain websites

If you find that Firefox can load some websites but not others, first clear your Firefox cookies and cache:

  1. Click the menu button New Fx Menu , choose History and select Clear Recent History....
  2. In the Time Range to clear: drop-down, select Everything.
  3. Click the arrow next to Details to display the list of items that can be cleared.
  4. Select both Cookies and Cache.
  5. Click Clear Now.

Check for malware

If clearing your cookies and cache did not enable you to load the websites that did not work in Firefox, you should check your computer for malware. Certain types of malware are known to target Firefox and can prevent it from loading various websites:




Based on information from Error loading websites (mozillaZine KB)

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Comments

For related discussion about this article and other KB articles involving connection issues, read /forums/contributors/534301

This article is one of the top twenty troubleshooting articles but is considered "failing", since its helpfulness rating is less than 50%.

See the related discussion:
/forums/knowledge-base-articles/707113 Focus on troubleshooting

I removed the fx35 tag, added a link to the article about malware, fixed outdated links and displaying issues, added a summary. It needs review.

It might be not enough to improve the helpfulness of the article. See /en-US/kb/Firefox%20cannot%20load%20w.../1660.

In the last section, you have:

* If you still have problems, follow instructions in the How do I get rid of malware? of Troubleshoot Firefox issues caused by malware.
 

I would either make it "section of" or just make it "follow the instructions in How do I get rid of malware?".

I'm not sure how to make this article more helpful except maybe to add a link to Troubleshoot and diagnose Firefox problems (like I did here). There are other suggestions in MozillaZine's article under Only Mozilla applications are having problems that should be checked out, especially the section on other security programs that may be blocking sites.

P.S. I would also rename the section, "Cannot load websites after updating Firefox" to "Security software blocking Firefox" to also cover situations in which changes made to security software (such as installing/enabling a "parental controls" component) causes the problem, as was the case here.

AliceWyman said

I would either make it "section of" or just make it "follow the instructions in How do I get rid of malware?".

I chose the second one in a new revision.

maybe to link to Troubleshoot and diagnose Firefox problems

I didn't. Indeed, in that case, we should add it in every troubleshooting articles.

There are other suggestions in MozillaZine's article under Only Mozilla applications are having problems that should be checked out, especially the section on other security programs that may be blocking sites.

It's already in the first section.

The first section is "Cannot load websites after updating Firefox ". It needs to be renamed (maybe "Security software blocking Firefox" or "Security software blocking websites") and edited to also cover cases where security software is added, updated, or reconfigured, which results in Firefox no longer being able to load some or all websites.

AliceWyman said

The first section is "Cannot load websites after updating Firefox ". It needs to be renamed (maybe "Security software blocking Firefox" or "Security software blocking websites") and edited

Indeed, there's a dedicated Fix problems connecting to websites after updating Firefox article for the updating case, and this one must be more generic. I updated the first section.

I removed the win tag for the malware section. Indeed, malware can target Firefox on Mac OS X or Linux.

It needs review.

Approved.

An update to this article was approved today. Hopefully this will improve the article's helpfulness.

LexieMac

Sorry to say Firefox Support has become very awkward to navigate. It's a maze.

If I'm in the wrong place, please post a link.

I can open websites. But Fandango.com specifically won't play movie trailers and videos in Firefox browser.

I could not play video's on Fandango.com in Firefox before updating to the latest FF v 40 something. Updating to the latest version of FF didn't help.

I updated, flash player, java etc nothing works for that site. Youtube and video on other sites are working.

The videos on Fandango work in IE11 so I'm really baffled as to what is causing it and what to do.

Thanks for any help.

LexieMac said

Sorry to say Firefox Support has become very awkward to navigate. It's a maze. If I'm in the wrong place, please post a link. I can open websites. But Fandango.com specifically won't play movie trailers and videos in Firefox browser. I could not play video's on Fandango.com in Firefox before updating to the latest FF v 40 something. Updating to the latest version of FF didn't help. I updated, flash player, java etc nothing works for that site. Youtube and video on other sites are working. The videos on Fandango work in IE11 so I'm really baffled as to what is causing it and what to do. Thanks for any help.

As you figured, this forum is not the place for getting help with Firefox. You'll have to ask your question again in the support forum. See Get community support. I'll close this thread.