This site will have limited functionality while we undergo maintenance to improve your experience. If an article doesn't solve your issue and you want to ask a question, we have our support community waiting to help you at @FirefoxSupport on Twitter and/r/firefox on Reddit.

Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

what is address not understood?

  • 3 replies
  • 1 has this problem
  • 1 view
  • Last reply by cor-el

more options

what is with this new "this address wasn't understood" and how do i get rid of it?

what is with this new "this address wasn't understood" and how do i get rid of it?

All Replies (3)

more options

It would help to know what address that was.

Maybe you mistyped it.

more options

Hi   !

Is the full message :

"The address wasn’t understood Firefox doesn’t know how to open this address, because one of the following protocols (javascript) isn’t associated with any program or is not allowed in this context. You might need to install other software to open this address."


If so, would you do this please : Type in the address bar   about:config  (press Enter) (promise to be careful, if asked) And type and look for the preference : network.protocol-handler.external.javascript and make sure that its value is set to   false   (= default)

more options

Do you use a bookmark or are you starting with the main (home) page of this website?

If you use a bookmark then navigate to the web page starting with the main page or the sign in page in case there is a problem with this bookmark.


You can try these steps in case of issues with web pages:

You can reload web page(s) and bypass the cache to refresh possibly outdated or corrupted files.

  • hold down the Shift key and left-click the Reload button
  • press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux)
  • press "Command + Shift + R" (Mac)

Clear the cache and remove the cookies from websites that cause problems via the "3-bar" Firefox menu button (Options/Preferences).

"Clear the cache":

  • Options/Preferences -> Advanced -> Network -> Cached Web Content: "Clear Now"

"Remove the cookies" from websites that cause problems.

  • Options/Preferences -> Privacy -> "Use custom settings for history" -> Cookies: "Show Cookies"

Start Firefox in Safe Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration is causing the problem.

  • switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Appearance
  • do NOT click the "Refresh Firefox" button on the Safe Mode start window