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

Boxes with hex codes instead of characters even in Start Page

  • 12 replies
  • 8 have this problem
  • 157 views
  • Last reply by juanmpd

more options

Suddenly I have started experiencing a weird problem with Firefox. I’m using the last version up to date, 56.0 (64-bit), on a Windows 7 system. Firefox seems unable to render any character, even in its own start page. It instead shows boxes with hex codes. One weird thing is that, if a save the page to disk, I can open it and then all the characters are shown correctly.


After doing some research on the internet, I have tried the following to no avail: - Checking I had checked the option ‘Allow pages to choose their own fonts, instead of your selections above’, under Options > General > Font&Colors > Advanced… This was not really necessary, as I never change Firefox font related default settings, but I rechecked just in case… - Disabling all add-ons and complements. - Removing all previous Firefox Profiles. - Uninstalling Firefox completely, then installing it again. - Restarting Windows in Safe Mode, then starting Firefox in safe mode (holding SHIFT while starting Firefox) I use many other programs and applications, none of them showing any issues. In the meantime, I have been forced to quit Firefox and switch to Google Chrome and Internet Explorer.

Suddenly I have started experiencing a weird problem with Firefox. I’m using the last version up to date, 56.0 (64-bit), on a Windows 7 system. Firefox seems unable to render any character, even in its own start page. It instead shows boxes with hex codes. One weird thing is that, if a save the page to disk, I can open it and then all the characters are shown correctly. After doing some research on the internet, I have tried the following to no avail: - Checking I had checked the option ‘Allow pages to choose their own fonts, instead of your selections above’, under Options > General > Font&Colors > Advanced… This was not really necessary, as I never change Firefox font related default settings, but I rechecked just in case… - Disabling all add-ons and complements. - Removing all previous Firefox Profiles. - Uninstalling Firefox completely, then installing it again. - Restarting Windows in Safe Mode, then starting Firefox in safe mode (holding SHIFT while starting Firefox) I use many other programs and applications, none of them showing any issues. In the meantime, I have been forced to quit Firefox and switch to Google Chrome and Internet Explorer.
Attached screenshots

Chosen solution

Have you checked this :

Press the Alt key and at the upper left click on View => Textencoding  ?

As you have tried just about everything else, let's give this a try :

Type in the address bar about:config (press Enter) Promise to be careful, if asked) Type and look for the preference : security.sandbox.content.level and set its value to 1 (one) (default value is 3 )

This works for the question marks and letter 'A' in boxes - but if it doesn't work here, please change the value back.

Read this answer in context 👍 6

All Replies (12)

more options

One more try, again unsuccessful... I've uninstalled again Firefox, then I've done a search over the windows registry, deleted all mozilla/firefox related stuff, then delete some remnants of files and folders to make sure nothing remained in AppData/Local/Mozilla, AppData/LocalLow/Mozilla, AppData/Roaming/Mozilla, Program Files/Mozilla Firefox, Program Files(x86)/Mozilla Firefox... Then installed Firefox. But the same issue was there...

more options

I post again the attached image, as I'm not sure it was previously successfully uploaded.

more options

Would you please check this setting :

Type in the address bar about:config (press Enter) (promise to be careful, if asked) Type and look for the preference : gfx.downloadable_fonts.enabled and make sure that its value is set to true

more options

Enigma said

Would you please check this setting : Type in the address bar about:config (press Enter) (promise to be careful, if asked) Type and look for the preference : gfx.downloadable_fonts.enabled and make sure that its value is set to true

Yes, it is set to True. I suspect this preference corresponds to the option ‘Allow pages to choose their own fonts, instead of your selections above’, under Options > General > Font&Colors > Advanced… , which I had previously reviewed

more options

Chosen Solution

Have you checked this :

Press the Alt key and at the upper left click on View => Textencoding  ?

As you have tried just about everything else, let's give this a try :

Type in the address bar about:config (press Enter) Promise to be careful, if asked) Type and look for the preference : security.sandbox.content.level and set its value to 1 (one) (default value is 3 )

This works for the question marks and letter 'A' in boxes - but if it doesn't work here, please change the value back.

more options

Enigma said

Have you checked this : Press the Alt key and at the upper left click on View => Textencoding  ? As you have tried just about everything else, let's give this a try : Type in the address bar about:config (press Enter) Promise to be careful, if asked) Type and look for the preference : security.sandbox.content.level and set its value to 1 (one) (default value is 3 ) This works for the question marks and letter 'A' in boxes - but if it doesn't work here, please change the value back.

About 'View>Textencoding', it is dissabled on the Firefox Start Page, which displays wrongly. If loading a web page such as 'google.com', It shows 'Unicode'.

But changing 'security.sandbox.content.level' as you suggested to '1' has solved the issue! Thank you very much! I had seen this problem about question marks but I had disregarded it, because I thought it was unrelated...

more options

Yay  ! So glad that worked  !

more options

Just for the record...

I'm not currently using Firefox, as I'm a bit cautious about lowering security.sandbox.content.level from 3 to 1.

Nevertheless, I wondered if Firefox Developer Edition would show the same behaviour, so I downloaded and installed it [57.0b8 (64-bit)].

It directly crashed on opening, showing a message "Gah. Your tab just crashed.", with Windows poping up a dialog about an "unknown software exception (0xc000001d) at address 0xd235ca86. This message showed again on trying to create any new tab. But the address bar was accessible. So I tried to enter several website urls, getting the same error.

Then I tried entering a local html file, and It displayed correctly. Then I entered 'about:config' at the address bar, and I changed security.sandbox.content.level value from 3 to 1. With this change, the problem disappears in Firefox DE.

Conclusion: the problem I've reported may remain in future versions of Firefox, thought with different symptoms.

more options

Hi juanmpd, thank you for the additional information.

By default, Firefox on Windows 7 uses a system font named Segoe UI for those characters you saw as boxes on the built-in home page. This should be no problem to access with the stronger content sandbox. However, the sandbox affects several other considerations, so if you are using the default font, it might be something else.

Can you use Firefox's Inspector to check the font used on the built-in home page? You can right-click some text and use Inspector Element. This should open the Inspector in a panel in the lower part of the tab. Then on the right half of the panel you can choose the Fonts pane (you might need to use the small triangle at the right end to get to Fonts). Is it Segoe UI?

more options

Thank you for your interest... especially as this problem seems to have been reported only by me, and it has the workaround pointed by Enigma [changing 'security.sandbox.content.level' as you suggested to '1'] I suppose it only shows up after a series of circumstances we won't be able to isolate... In any case, following your directions I've uninstalled Firefox Developer Edition and installed again 'standard' Firefox on my Windows. I've checked the Start Page as appointed, and I've also saved it to disk, to open as a local file. I've attached an image showing the results:

  • The start page uses 'MT Extra system', not Segoe UI.
  • The start page, if saved to disk and then opened locally, do indeed uses Segoe UI as you supposed.

-- One more thing... I have looked my installed fonts, and 'MT Extra' was the only installed in a different place (C:\Program Files (x86)\Common Files\microsoft shared\EQUATION). Just to try, I uninstalled this font. Then, if I open Firefox again, then I can see the start page tries to use EmojiOne Mozilla system, with the same display result of boxes with hex codes...

Modified by juanmpd

more options

It's very odd. The page should use the font that Windows says is the system font.

font-family: -moz-use-system-font;

I don't know why that works on the saved page but not in the live page.

more options

Thank you anyway for your interest!