Known issues in the current version

Development notes

The Pale Moon browser, at any point in time, may have a number of known issues. These known issues will usually be addressed in the next release of the browser, or it may be something that people have noticed and are mentioned here because they are "by design", i.e.: issues people have asked about, are known, and are this way on purpose.
For each issue, check the status for intended action to be taken in development (if any) and intended timeline (if applicable).

Known issues in the current version:
  1. Pale Moon may crash on pages with multiple auto-playing videos
    This is caused by an issue in the new media code we introduced currently not handling rapid starting/stopping and concurrent playing of multiple videos well. This may in some cases also cause a hard hang or lock-up of the browser.
    Status: [Fixed]
    Workaround: Set media.autoplay.enabled and media.autoplay.allowscripted to false in about:config and restart the browser. This will stop the crashes, but obviously also prevent auto-play of videos on pages.
    Timeline: Fixed in 27.1.1.
  2. After upgrading from v26 and earlier to v27, stored passwords are missing
    If you have previously copied a (newer) Firefox profile to Pale Moon that already uses the new password storage format, and this was previously converted from the older format, then it's possible that Pale Moon 27 will not convert your stored passwords properly (because a new storage file already exists).
    Status: [Workaround]
    Please see this FAQ for steps to recover from this situation.
  3. After upgrading to v27 from a localized browser setup, it will not start
    If you get a small window with an XML parsing error instead of the normal browser interface, your language pack was not properly disabled as it should. V26 language packs are not compatible with v27 and will prevent the browser from starting.
    Status: [Workaround]
    Please see this FAQ for steps to recover from this situation.
  4. A number of Firefox extensions do not work
    This is caused by Pale Moon's divergence from Firefox. Please see the forum and our own add-ons site for replacements/alternatives.

Known issues in all versions:

  1. The browser creates directories under %APPDATA%\Mozilla, specifically Mozilla\Extensions
    These directories are related to the underlying Mozilla extension code (Pale Moon is a Mozilla-derived browser) and stores extension IDs there. This issue is completely harmless and non-breaking; in fact, having (all) Mozilla-based applications use this one central location for extension IDs is desired.
    Status: [By Design]

Known issues in previous versions

Because issues in previous versions may still apply to what people are running, here is a recap of previous, still recent versions that have been fixed, and potential workarounds:

  1. doesn't work
    Pale Moon 27.0.0 is unable to play videos. This is a problem with the added MSE routines and continued work on media playback changes.
    Status: [Fixed]
    Workaround: Go to Options -> Content, and uncheck "Enable Media Source Extensions (MSE)"
    Timeline: Fixed in 27.0.1
  2. After upgrading some tabs' content doesn't want to load
    On some systems, the contents of a portion of automatically restored session tabs doesn't want to load when clicked and needs a manual reconfirmation of the URL. This is caused by a combination of things happening with the one-time profile migration with the upgrade to 27.
    Status: [Fixed]
    Workaround: Please see this FAQ for a workaround to solve the session store problem.
    Timeline: Fixed in 27.0.3
  3. Pale Moon x64 refuses to install on Windows Vista
    This is due to an incorrect check that came across from the Mozilla platform when we updated it for v27.
    Confusingly, it will tell the user that it requires Windows Vista x64 (while the check requires at least Windows 7)
    Status: [Fixed]
    Workaround: Install the 32-bit version
    Workaround (alternative): Install from the ZIP archive
    Timeline: Fixed in 27.1.0

  1. HTTPS proxies are not supported
    We currently do not have support for encrypted connections to proxy servers.
    Workaround: If you need local-net encryption (untrusted local network) then you should use an encrypted VPN connection instead of a proxy server.
    Status: Solved in v27.
  2. JavaScript "promises" are not supported
    We currently do not support a spec-compliant version of so-called "promises" in JavaScript (part of ES6). As such, some sites that explicitly rely on this and that do not properly check for this feature or don't provide one of the many polyfills for it that are available on the server side, will fail to function properly (and in some cases even completely fail to display).
    Fix: Ask the website owners to include proper feature detection and a promises polyfill.
    Workaround: For some sites, our promises injector extension may work. Please note that fixing some sites with this may break other sites in turn (because the extension isn't implementing the entire spec, and properly-detecting sites will assume promises are fully available)
    Status: Solved in v27.

  1. On Windows 10, if you have the classic menu bar enabled, it may be white-on-white
    This is due to Windows 10 apparently not always setting the proper registry entries for applying color to the Windows UI.
    Status: [Fixed]
    Workaround/Fix: Go into "personalization" of your desktop, Select "color" on your left, and toggle the slider "Show color on Start, taskbar, action center, and title bar" on and back off again. This will make the proper registry entries. Exit and restart the browser to have it pick up the value.
    Timeline: Fixed in 26.3.3
  1. On Windows 10, if you have the classic menu bar enabled, it may be white-on-white
    This is due to a small issue in the new Windows 10 user interface in Pale Moon adapting to a chosen accent color, but Windows not having an accent color set in the registry.
    Status: [Fixed]
    Workaround/Fix: Go into "personalization" of your desktop, Select "color" on your left, and choose an accent color to use for your windows. This will make the proper registry entries. Exit and restart the browser to have it pick up your new choice.
    Timeline: Fixed in 26.3.2
  1. On some sites, pressing "back" may occasionally cause a browser crash
    On some specific sites, using the browser's "back" button/navigating back in history may cause the browser to crash. This is caused by an issue in the XSS filter.
    Status: [Fixed]
    Workaround: Disable the XSS filter in options
    Timeline: Fixed in 26.3.0
  1. Keyboard navigation of the user interface doesn't properly work
    With 26.2.0, trying to navigate the application menus with the keyboard doesn't work.
    This is caused by the change in keystroke handling in this version negatively affecting how they are handled in the UI as well.
    Status: [Fixed]
    Workaround: None, unfortunately. Use your pointing device.
    Timeline: Fixed in 26.2.1.
  1. Animated GIF files may cause performance issues
    We are aware of performance issues on Windows for animated GIF images being used as "pseudo video". particularly large animated GIF files or a large number of these "video" GIFs on a single page may slow down the browser (in some cases severely) and cause high CPU usage.
    Cause: This is likely an issue with the way Pale Moon tries to perform rapid memory allocations and the Windows system memory allocator in particular not handling this (atypical) behavior very well.
    Status: [Fixed] - We'll be using a more Mozilla-code-friendly allocator library.
    Timeline: Fixed in 26.1.0
  2. Google Hangouts doesn't work
    The website versions of Google Hangouts (either stand-alone or integrated in Google+) don't work because they won't let you sign in to your account.
    Cause: unknown, server-side issue
    Status: [Fixed]
    Workaround: None, use the Hangouts App or Google Chrome
    Timeline: Fixed in 26.1.0

  • The browser doesn't start with "Unsupported operating system"
    Windows XP users who have hacked their OS with a registry hack to supposedly "get continued security updates" from Microsoft past the end-of-life date for Windows XP in 2014, by tricking the Windows Update servers into thinking that they are running Windows Embedded (a bad thing to do, see articles on Neowin, Tom's Hardware and Betanews) will be unable to start the browser.
    This is caused by a sanity check in the browser for supported operating systems (since we do not support point-of-sale or embedded Windows versions due to technical compatibility issues with those SKUs) to prevent problems on platforms that are not a valid target for Pale Moon.
    By user request, we've decided to remove this check with the clear responsibility for support being shifted to end-users. You are on your own when not running a straight-up retail/OEM Windows XP.
    Status: [Fixed]
    Workaround: Remove the registry hack
    Timeline: Fixed in 26.0.1
  • The browser has a number of web compatibility issues
    Some well-known sites don't like the "Goanna" user agent and/or are specifically blocking Pale Moon.
    Status: [Workarounds] by way of user agent overrides for YouTube, Netflix, some fora, etc.
    Timeline: Ongoing, some major sites fixed in 26.0.1

  • When playing videos in fullscreen mode, you may see network status pop up
    This is because a number of major sites have changed the way videos are embedded in pages, which isn't properly detected by Pale Moon when switching to fullscreen mode, resulting in the browser treating it like a normal fullscreen mode web page.
    Status: [Fixed]
    Workaround: Go to (Options ->) Status bar options... -> Advanced -> uncheck "Detect full-screen mode and show links/status appropriately"
    Timeline: Fixed in Pale Moon 26.0
  • When running on Windows 10, there are some theming/UI issues
    These issues include wrong shapes of the window control buttons, them being off-center, strange background color issues in the bleached white application areas (e.g. when opening a sidebar) and border drawing issues.
    This is caused by the changes Microsoft has made (a lot of them at the last second) to the way windows are drawn and handled. This is known and work is underway to correct these issues.
    Status: [Fixed]
    Workaround: None
    Timeline: Fixed in Pale Moon 26.0
  • The internal updater won't show proper text in the default language
    Because of a localization error, the text in the internal updater window will not show properly when an update is offered to the browser. You can still update normally by pressing the "Next" button.
    Status: [Fixed]
    Workaround: none
    Timeline: Fixed in the 25.6 updater.
  • Android: using VPN connections may not work
    If you are using a VPN connection on Android 5 (Lollipop), Pale Moon may not be able to resolve host names, leading to connectivity failures. This is caused by a known problem in the underlying Fennec code that caters to much older versions of Android and relies on functions that have been removed in Android 5.*
    Status: [Fixed]
    Workarounds: Use local (on-device) DNS resolution with a DNS resolver, use a different browser for VPN use, or downgrade to Android 4.*
    Timeline: Fixed in 25.4
  • Some Single-Sign-On (SSO) setups don't work
    Because of a security vulnerability with authentication redirection (cookie injection) through proxies (CVE-2014-8639 MFSA2015-04), Pale Moon currently does not allow auth cookies to pass through or be modified by proxies. This may make some SSO setups fail to authenticate to individual services (usually on corporate intranetworks that employ proxies) and as a result the user is asked to provide login details.
    Status: [Fixed], following the relevant Mozilla bugs.
    The vulnerability patch was adapted to allow for cookies to be stored by authenticating proxies, but not on proxy connection failures, greatly reducing the available scenarios for this already difficult to practically exploit session fixation vulnerability. It should be sufficiently mitigated this way while not being in the way of legitimate cookie injection requests. In environments where this is a concern, the session policies should be revised or implemented in a different way.
    Workaround: Avoid using proxies for SSO.
  • Add-on update checks don't work
    This is caused by a hidden, undocumented feature in the Mozilla code that requires a very strict check on the certificate presented by the add-ons server.
    Status: [Fixed]
    Workaround: Create a new boolean preference called extensions.update.requireBuiltInCerts and set it to false
    Timeline: Fixed in 25.0.2
  • Some parts of Devtools don't work
    This is caused by the rather unexpected in-app useragent sniffing that the devtools do (yes, seriously!)
    Without Firefox/* in the UserAgent string, the JavaScript debugger and Style Editor (and possibly a few other functions) don't work properly or at all.
    Status: [Fixed]
    Workaround: Set general.useragent.compatMode.firefox to true
    Timeline: Fixed in 25.0.2
  1. Some jetpack add-ons that should work refuse to work properly
    This is caused by some add-on SDK files missing the new Pale Moon ID in them.
    Status: [Fixed]
    Timeline: Fixed in 25.0.1
  1. Rendered text color may become the wrong color or white when scrolling
    In some situations, colored fonts may become the wrong color or white when scrolling and hardware acceleration is enabled in the browser.
    Workaround: set layers.force-active to true in about:config
    Status: [Fixed]
    Timeline: Fixed in 24.7.1
  2. Google Maps on displays a non-functional preview of the "new" maps.
    This is caused by interpretation of the custom user agent in Pale Moon for the domain.
    Workaround: see
    Status: [Fixed]
    Timeline: Fixed in 24.7.1
  1. Domain highlighting sometimes works and sometimes doesn't
    This is caused by a conflict with domain highlighting and the code to have status indicators in the address bar.
    Workaround: Disable domain highlighting in the status bar options
    Status: [Fixed]
    Timeline: Fixed in 24.7.0
  1. After upgrading from 24.5 or before, the browser may crash on startup
    On systems where people have previously changed the advanced preference "" or "", 24.6.0/24.6.1 may crash or immediately close upon startup.
    This is caused by a multi-tiered problem in graphics engine selection, which sometimes causes an invalid or incompatible choice to be made by the browser.
    Workaround: Start the browser with SHIFT held down, and in the safe mode dialog box, click "Reset all user preferences to Pale Moon defaults" and then click "Make changes and restart"
    Workaround 2: Start the browser in safe mode (Start with SHIFT, then click "Continue in Safe Mode"), and manually reset all gfx.* preferences in about:config
    Workaround 3: Start the browser in safe mode, and set gfx.direct2d.disabled to true in about:config
    Workaround 4: Start the browser in safe mode and perform a browser reset from the Help -> Troubleshooting information page.
    Status: [Fixed]
    Timeline: Fixed in 24.6.2
  1. On certain systems, rendering of text and graphics may become "pixelated"
    If you are using Windows 7 SP1 with the (Feb 28th 2013) Windows Platform Update (KB 2670838), or potentially also if you are using Windows 8/8.1, and your system is equipped with a certain legacy ATI/AMD Radeon (specifically an HD3000 or HD4000 series) graphics processor, you may encounter issues with rendering text and graphics in page content, similar to:

    This is caused by the combination of OS, the Platform Update which makes changes to DirectX, and the graphics hardware/drivers in your system. Unfortunately, it's not clear who exactly is to blame, as people keep pointing fingers to others (Microsoft, AMD, Mozilla). Note that the update may also have been installed as a prerequisite for using MSIE 10/11.
    Of note: Later versions of Pale Moon are less likely to display this error than Firefox, but it may still occur.
    See - TL;DR: uninstall KB2670838 or disable azure for content.
    Fixed in 24.6.0.
  2. On some Windows 8/8.1 systems, the browser regularly crashes
    This is caused by a problem in the Gecko rendering engine on the newer version of Direct2D (introduced in Windows 8, 8.1 and through the Platform Update of Windows 7) when hardware acceleration is used.
    Status: [Fixed]
    Timeline: Fixed in 24.6.0.
  1. On some sites, the plugin notification icon may incorrectly show or provide a blank doorhanger
    This is caused by page content removing document nodes and confusing the plugin indicator code. As a result, you will see the following when clicking the plugin indicator:
    Workaround: None
    Status: [Fixed]
    Timeline: Fixed in 24.5.
  1. The download manager panel may pop up in the far bottom-left
    On some installations, the download manager panel may possibly pop up on the bottom left of the browser instead of where the download manager button is. This is caused by a small issue in the default set of controls in the v24.4.0 updated status bar code, confusing the panel by having 2 places to "hang" the panel from.
    I will be fixing this by removing the status bar download control from the "default" set of controls (like in previous versions).
    Workaround: Open the customization window (right-click a toolbar button and select Customize... from the menu) and remove the download manager control you don't intend to use (either the button in the main navigation bar or the control in the status bar) by dragging it from the browser window to the customization window.
    Status: [Fixed]
    Timeline: Fixed in 24.4.2.
  1. Trying to open up the download manager from the download status control doesn't work
    Trying to open up the download manager (either panel or classic window) by clicking on the status bar control for downloads does nothing. This is caused by a small issue in the newly updated status bar code in 24.4.0.
    Status: [Fixed]
    Timeline: Fixed in 24.4.1
  1. When using the classic downloads window, downloads in private windows are not shown
    If you use the classic downloads window and open a Private Browsing (PB) window, there is no easy way to see which downloads are done in the PB window. When checking the downloads, it will open up the (non-PB) classic downloads window which does not have downloads listed from the PB session.
    This is caused by PB windows being implemented after Mozilla moved to the panel-based downloads manager, and there is no check in the classic downloads window if it is called from a PB window or regular window.
    Workaround: In the PB window, open a new tab and type about:downloads in the address bar
    Status: [Fixed]
    Timeline: Fixed in 24.3.0
  2. Geolocation doesn't work in Pale Moon
    This is caused by the Firefox standard geolocation provider (Google Inc.) now requiring an API key to request geolocation coordinates. Only official Mozilla Firefox builds of the code will work.
    Pale Moon will be switching provider to address this issue.
    Workaround: none.
    Status: [Fixed]
    Timeline: Fixed in 24.3.0
  3. The "More information" link for blocked add-ons doesn't work
    Workaround: See
    Status: [Fixed]
    Timeline: Fixed in 24.3.0
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