The Pale Moon Project - Customly optimized and built Firefox browsers for Windows Operating Systems

Pale Moon: Troubleshooting


Of course, a complex piece of software like a web browser is not without its bugs or problems. Some people have raised some questions at my address, and I hope the information on this page will help you solve issues you may have.

IMPORTANT NOTE: The troubleshooting guide provided here is by no means complete, and serves mostly as an addition for Pale Moon specific problems to the otherwise excellent knowledgebase maintained by the Mozillazine team. If you have a specific technical problem (especially with profiles, settings, things not being saved/remembered) then please also check the Mozillazine knowledgebase. Pale Moon is built from Mozilla Firefox code, and common issues that are seen with the Firefox browser may also pop up for Pale Moon.

The Mozillazine knowledgebase can be found here:

Where these instructions tell you to use the about:config configuration editor, type that in the address bar and press enter, follow the instructions, and then (to be sure) close the browser completely and restart Pale Moon. This puts all changes made into effect.

Windows Media formats don't play in Pale Moon

This is a known issue with Firefox and Firefox-based browsers; it sometimes does not pick up the required dll files correctly to play embedded Windows Media video/audio. It seems to be an issue that occurs regularly on Windows Vista or later.

This can be solved by downloading the official "Interoperability Bridges" dll file you need here, then simply copying the files in that zip to Pale Moon's plugin folder (usually c:\pogram files\pale moon\plugins - if the "plugins" folder doesn't exist yet, create it!) and then completely exiting and restarting the browser.

A side note is that WMP video functionality is seeing a rapid decline with the broader adoption of plugin-less video playback (e.g. HTML5 Theora/WebM), quite often there are alternatives offered to using the WMP plugin on sites.

More information about this problem can be found in Mozilla's knowledge base:

Some sites or addons don't work with Pale Moon (unknown browser)

Some sites or addons check the Useragent of the browser you are using, which may cause them to come up with an "unknown" browser, and may either refuse access or present incorrect or broken code. Examples of such sites are Microsoft's Skydrive and the "new" Yahoo webmail. You may also run into XML errors, "XML Parsing Error: not well-formed" because of this. This is not necessarily a Pale Moon error, but rather an error server-side: it gives back badly formatted code when it doesn't recognise the browser and defaults to something that does not work in Firefox-based browsers (because it is not formatted correctly). This is especially the case for Microsoft web servers using Active Server Pages and a certain template, that will fall back to MSIE specific code (which is not standards compliant)

Version 3.6 only
: A workaround for this is to open the advanced configuration editor with about:config in the address bar, and to change the parameter general.useragent.extra.firefox to "Firefox/...", using a known Firefox version.
For example:
Change general.useragent.extra.firefox to "Firefox/3.6.9"

The browser identifies itself as Firefox-compatible by default: "Firefox/{version} PaleMoon/{version}". If you run into problems with sites not recognising Pale Moon with a correct version, it's probably because you have set a configuration parameter previously as a workaround, or some other piece of software has set or changed this value, retaining an incorrect identification for Pale Moon.

Alternatively, for web sites that strictly filter on only a few "known" browsers, you can try an addon like User Agent Switcher or similar to present websites with a custom browser identification.

Pale Moon has trouble with sites, buttons disappear and add-ons don't work properly

If you are running into really odd problems with Pale Moon like: buttons disappearing on some tabs, add-ons not working at all or not correctly, and similar curious and strange errors, you may be suffering from a corrupt user profile. This is a known problem, especially with having had previous versions of Firefox installed (the profile is usually retained when upgrading, including old settings that may not work). This problem can also occur with official Mozilla Firefox builds.

A known solution is to do the following:
  1. Backup your bookmarks and other things you want to save.
  2. Start pale moon with (from the command line): palemoon.exe -ProfileManager
  3. This opens up the profile manager window. Remove your current profile and make a new one.
  4. (optional) You can use this to also create separate profiles for different people using the same windows account, if you want, or for different purposes.
  5. Close the window and start Pale Moon.
This should fix these kinds of issues.

Pages don't load/stall or load slowly

Stalls on "Transferring data from..."
It may be that so-called "http pipelining", enabled by default in Pale Moon 3.6 and later, doesn't work well for your network settings, internet connection, or the particular web server you are trying to use (particularly the case with non-standard or older web servers). Try setting network.http.pipelining to false (in the advanced configuration editor about:config). Pipelining is still not considered mainstream, but works fine for 99% (or more) of the servers out there. I've encountered no problems having it enabled in Pale Moon, and it greatly improves network communications to sites with a lot of small elements on the pages, but it may not work for you.
Note: if you are having issues connecting through a proxy server, you should check here instead.

Stalls on "Waiting for..."
If Pale Moon seems to refuse to load pages from certain websites, getting stuck on "waiting for {website name}" at the bottom  (status bar) without displaying a page and an unending "Loading" in the tab header) but doing fine on others, and you have confirmed that it is not the web server having issues due to e.g. high load or connectivity problems, there are a few things you can try, by using the about:config advanced configuration editor. Use the search bar at the top to find the parameters indicated below, and double-click them to change betreen true or false or modify the value of them, or right-click them and select "reset" to reset them to default values.

Options you might want to look at are network.http.max-connections, network.http.max-connections-per-server, network.http.max-persistent-connections-per-proxy and network.http.max-persistent-connections-per-server
If any of these are indicated in bold typeface, it means they are not set to default values - try resetting them with a right-click. These values may have changed due to "tweakers" or "optimizers" for a previously installed Firefox, and be set to values that don't work for Pale Moon.

Other stalling while loading pages
This link may be helpful:

Pale Moon doesn't start, and gives an error message box

Make sure your system meets the requirements to run Pale Moon. The most common occurrence of this error is trying to run it on a PC that doesn't meet the system requirements. Specifically, you will get the error:

 "The application failed to initialize properly (0xc000001d). Click on OK to terminate the application."

If you have an old Athlon (Thunderbird, XP or MP) machine or a Pentium II or III, this browser will not run.

My RoboForm extension/RoboForm toolbar doesn't work (properly)

Current versions of RoboForm work fine in Pale Moon 4 and 5 if you install the "Lite" version, which is merely the Firefox add-on.
If you run into unreadable text on the toolbar (black on black), do the following:
  1. Open the advanced configuration editor (about:config)
  2. Find gfx.direct2d.disabled and set this value to true
This will impact the performance of the browser for some websites, but will enable proper use of the toolbar.

KeyScrambler doesn't work with Pale Moon

Upgrade KeyScrambler to or later to fix errors with Pale Moon. Previous versions of KeyScrambler do not support this browser.

If you still run into problems with "ksClass not defined" upon startup after upgrading, a possible workaround is to rename palemoon.exe to firefox.exe - KeyScrambler's script apparently does a "hard" check on the executable filename and throws an error if it is anything but "firefox.exe" - Something to be fixed by the people releasing KeyScrambler.

One of my add-ons / extensions gives an error

Unfortunately, there are a few select add-ons/firefox extensions that simply don't work with Pale Moon - this is a problem with the way the add-on is programmed. Most major add-ons that I know of are supported without any issues, so you'll have to see this as a trade-off for not using Mozilla Firefox. So far, I've had reports of the following few add-ons being problematic: Roboform, Firefox Throttle, Prism For Firefox, IE Tab +.

I prefer ctrl-tab / shift-ctrl-tab to page back and forward through tabs immediately

If you don't like the graphical preview pane, find it confusing to use, or have any other reason to use the Firefox standard Ctrl-Tab swapping between tabs, you can switch Pale Moon to use standard Ctrl-Tab / Shift-Ctrl-Tab paging:

go to about:config and set browser.ctrlTab.previews to false

My external program {xx} doesn't recognise/work with Pale Moon

This all depends on how the external program (e.g. download manager, etc.) is programmed. If you installed Pale Moon using a ZIP file, this may be the cause, as some programs check for Windows Registry entries that are normally made by the installer but aren't present if you just unpack a ZIP file - this is why it's recommended to use the installer when you can! Pale Moon itself works fine without the registry entries, by the way.

Another common cause for this is the fact that the external program has been written with only Firefox in mind, and uses so-called "hard-coded" names in the software to call Firefox specifically (e.g. looking for 'firefox.exe'). This will prevent the program from using Pale Moon, even though it could possibly work otherwise, since the program doesn't recognize Pale Moon as a known program. This can only be fixed by the developers of the external program.

Pale Moon is not available in my preferred language

Pale Moon is released as a US-English browser, and there are no localized installer versions for other languages available. If you feel more comfortable with a different localization of the browser for menus and user interface, there is an option to change the elements of the browser interface to match your preferred language using a language pack. I have not personally tested all of these language packs and there may be problems with some of them. Use them at your own risk!

How to install a language pack for your language:
Go to the "Language packs" section of this website and follow the instructions found there.

Pale Moon no longer scans downloaded files when completed

Starting with 3.6.3, the code for the "on-download completion scanner" has been completely removed, because it caused unnecessary delays with it sometimes triggering wrongly (e.g. when no AV scanner installed, still trying to scan) and overall instability with the AV-scanner Windows API. Your resident ("on-access") AV scanner should still pick up on any dangerous files with this disabled.

The Pale Moon profile migration tool (for 3.6.6 or later) doesn't work

Since there are many different setups of Windows, it is always possible that the migration tool doesn't do its job properly. In that case, you will have to manually copy your user profile(s) to the proper location for Pale Moon 3.6.6 or later. You can also use this method to manually copy a Firefox profile to be used in Pale Moon (they are compatible). Close down the browser and do the following:
  1. Find your old Pale Moon/Firefox profile folder. Usually:
    On XP: C:\Documents and Settings\{your user name}\Application data\Mozilla\Firefox
    On Vista/7: C:\users\{your user name}\Application data\Mozilla\Firefox
  2. Copy everything in that folder (subfolders and profiles.ini) to Pale Moon's profile folder, overwriting what is there. If you have already run Pale Moon at least once, it will have created the folder structure already:
    On XP: C:\Documents and Settings\{your user name}\Application data\Moonchild Productions\Pale Moon
    On Vista/7: C:\users\{your user name}\Application data\Moonchild Productions\Pale Moon

Windows error opening an internet shortcut or local HTML file

If you receive an error trying to open an internet shortcut or local HTML file stating "file not found" or "There was a problem sending the command to the program" (but the file or URL/file still opens in Pale Moon), the file/protocol handlers have not been registered correctly. This is not a problem with the browser itself but usually caused by incorrect registry entries made by the installer (e.g. the installer of 3.6.8).

If you are on Windows 2000 or Windows XP, the following Mozilla KB article provides a solution:

If you are on Windows Vista or Windows 7, you will have to edit the registry to correct this problem.

You can download a quick fix here, simply double-click the .reg file and it will make the registry entries for you.

Alternative: If you want to do it manually, follow the instructions below:

Caution: Editing the registry incorrectly can damage your system. Do not attempt these steps if you are inexperienced or uncomfortable using the Registry Editor.

   1. Go to "Start -> Run" (or press the windows key+R) then type regedit and click OK
   2. Use the directory tree hierarchy to navigate to "HKEY_CLASSES_ROOT\HTTP\shell\open\ddeexec"
   3. Delete the "ddeexec" registry key
   4. Repeat for "HKEY_CLASSES_ROOT\HTTPS\shell\open\ddeexec" (and any other protocols you want to fix)
   5. Repeat for "HKEY_CLASSES_ROOT\FirefoxURL\shell\open\ddeexec"
   6. Repeat for "HKEY_CLASSES_ROOT\FirefoxHTML\shell\open\ddeexec"
   7. Repeat for "HKEY_CLASSES_ROOT\htmlfile\shell\open\ddeexec"

Problematic extensions can also cause the issue, including the Google Toolbar for Firefox  and possibly others (disabling or uninstalling the Google Toolbar extension will stop the error if not caused by some other toolbar). To see if an extension is causing the issue, try updating all extensions ("Tools -> Add-ons -> Extensions -> Find Updates") in case the problem has been fixed in the latest version. If the problem continues, you can disable or uninstall individual extensions to see if one of them is responsible.

Pale Moon keeps asking to be the default browser

Symptom: After installing or upgrading, you will get a dialog box every time Pale Moon starts, asking you if you want to make it the default browser.

For some reason, it seems that sometimes, specific Windows installations insist on not properly registering Pale Moon as a default browser. This can also occur in Mozilla's Firefox. The browser is default in that case, but Windows still reports that a different program is registered to handle links/shortcuts/protocols.
This seems to be more common on 64-bit windows versions (especially Windows 7) than on 32-bit ones.

There are a few potential workarounds for different causes (locked files, a missing profile, a problem with your default profile, etc.) but the easiest solution is to simply uncheck the checkbox in Options -> Advanced -> System defaults, "Always check to see if Pale Moon is the default browser on startup"

In some rare cases, running the Pale Moon installer as Administrator may solve this issue.

If it really doesn't set it as the default browser (and clicking a local file or internet shortcut opens a different browser), then you might have some file corruption going on or have preferences not saved or applied.

Some helpful links related to this issue:

Synaptics touchpad finger gestures don't work

If you have a Synaptics touchpad, e.g. on your laptop, and your 2/3-finger gestures don't work, try importing the following registry file to your windows registry. (Thanks to N.E. Goedhals for supplying me with the information!)
Download the fix here. Simply double-click the .reg file and it will make the registry entries for you.

Scrolling with my touchpad doesn't work

This is caused by the fact that the touchpad drivers don't know Pale Moon, and require an entry for each individual supported application. Until the touchpad manufacturers support Pale Moon by themselves, there is a workaround:
  1. Find the file tp4table.dat.
    For Synaptics usually in %ProgramFiles%\Synaptics\SynTP
    For Alps usually in %ProgramFiles%\Apoint2K
    You may need to look for it in another location if you have a different manufacturer.
  2. Open it with Notepad and add the following lines, make sure they are above the "Pass 1" rules:
    ; Pale Moon
  3. (optional) You can also add the extra lines below for additional scroll funtionality:
Thanks go to Allan and Chris for the solution!

The text on webpages looks blurry

This is caused by the fonts being rendered by your graphics card/drivers and not by Pale Moon. This may not look very nice, depending on the setting of your graphics drivers (especially if you have antialiasing force-enabled or similar).  DirectX isn't necessarily designed to  provide crisp detail rendering.

If you dislike how your GPU renders fonts you have the following options:

First and foremost, try to disable DirectWrite, this acceleration option for graphics seems to be poorly supported on especially integrated graphics (meaning a lot of laptop users and other people who don't have a dedicated graphics card):

In about:config, set gfx.font_rendering.directwrite.enabled to false

>> This is the default setting for this option since Pale Moon 4.0.3.

Other options, if you still have trouble:
  1. Tell your graphics card to not apply AA/AF/whatever it takes on Pale Moon.
    A control panel for your card should be able to do this, ideally. OR
  2. This might need to be done work in conjunction with #1.
    There's an addon to tweak the post processing that is applied to the fonts:  OR
  3. In case those don't work, or you don't want to bother messing around with the GPU rendering, you can tell Pale Moon to use the "normal" font rendering (CPU based).
    • Check your options, make sure that Hardware Acceleration is on
    • Navigate to about:config in the address bar
    • Type "2d" in the search field to quickly find "gfx.direct2d.disabled". Set this to true
    • Restart Pale Moon.

      If this still doesn't it work, set the following:
      (you can type in "font_render" to make them all show up)
    • gfx.font_rendering.cleartype.always_use_for_content to true
    • gfx.font_rendering.cleartype.use_for_downloadable_fonts to true
    • gfx.font_rendering.directwrite.enabled to false
    • gfx.font_rendering.directwrite.use_gdi_table_loading to false
    • Restart Pale Moon
Worst-case scenario, completely  turn off Hardware Acceleration in the options in addition to doing the rest of #3.
This shouldn't be necessary, though, and will have an impact on performance and functionality. Use only as a last resort.

Sources used for this entry:
And several different forums discussing this problem in Firefox.

Pale Moon doesn't work properly through my http proxy

Some proxy servers, like M86 Security's "Vital Security" proxy/gateway, don't handle http pipelining very well, resulting in some pages not loading correctly or at all, or causing broken images on pages or pages that never completely finish loading. To work around this problem, open about:config from the address bar, and type "pipelining" to quickly find the right setting.

Set network.http.proxy.pipelining to false

And restart your browser.

The status bar doesn't work (it remains blank)

In some cases, the status bar add-on might not initialize properly (e.g. after migration of a profile or when you have inadvertently mixed runs of version 3 and version 4 or later of the browser).
It will remain blank and act pretty much like the Mozilla add-on bar with nothing in it.

To fix, you have to reset a parameter:
  1. Open the configuration editor about:config
  2. Find the parameter status4evar.firstRun
  3. Set this parameter to true
  4. Exit and restart the browser
This should properly re-initialize the status bar.

Also, if you have migrated a profile from Firefox and were previously using the "status-4-evar" add-on on Firefox, then please remove "status-4-evar" and leave "Pale Moon statusbar" enabled. Since they are based on the same code, they will interfere with each other.

I use Windowblinds and Pale Moon is unusable

Pale Moon is incompatible with Stardock's Windowblinds' skinning engine when hardware acceleration is on. This is a rather hard conflict that makes the pages flicker and scrolling impossible.

There are 2 possible solutions:
  1. Put Pale Moon on the Windowblinds "exclusion" list to prevent the Pale Moon window from being skinned.


  2. Disable hardware acceleration in Pale Moon (Tools -> Options -> Advanced -> Uncheck "Use hardware acceleration where possible"

When I print, no text is printed, only images

Pale Moon 4 and later may, on some systems with some printers, have issues printing text when the text is rendered using accelerated graphics for fonts.
Try disabling hardware font rendering, in about:config set:
  • gfx.font_rendering.directwrite.enabled to false
  • gfx.font_rendering.directwrite.use_gdi_table_loading to false

    if still an issue after this, set:
  • gfx.direct2d.disabled to true
If that also doesn't work, you may have to disable hardware acceleration completely to solve the printing issue: Tools -> Options -> Advanced -> Uncheck "Use hardware acceleration where possible"

My problem isn't listed!

If your problem is with a plugin or extension, there's not much I can do about it. I didn't write the plugin or extension, nor the interface with it. If the problem you ran into is also present in Firefox with the same version, I may or may not be able to provide a fix or workaround - it all depends on the issue you have.

More information on general/common problems with firefox browsers can also be found in the Mozillazine knowledgebase:

If your system meets the requirements and otherwise runs fine for browsing, please let me know by using the contact form. You can use the same form if you think the problem might be able to be fixed using configuration and/or build options. Please describe the problem in detail. You may also want to consider posting your problem on the forum to get help from developers and fellow users.

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