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 time line (if applicable).


Known issues in the current version:
  1. Remote X rendering on Linux is slow
    We are currently investigating the exact cause, and have received offers to assist by the X2Go team to find the cause and solutions for slow remote rendering, even with xrender extensions present and in use. This may take some time to research and for a fix to be implemented and tested.
    Status: [In Progress]
  2. 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:

28.0.0(.1):
  1. Performance issues on all platforms, but especially 32-bit operating systems.
    Pale Moon 28 (especially if running on 32-bit operating systems) may display excessive CPU usage and slow performance or hangs.
    This is caused by a pair of Mozilla patches that were adopted in our browser as a defense-in-depth measure, but are causing some severe issues in terms of performance and reliability of the resulting browser.
    Status: [Fixed]
    Timeline: Fixed in 28.0.1
27.8.0:
  1. In some configurations, the browser may crash on shutdown.
    It seems to be especially the case if the Firefox version of GreaseMonkey (1.15) is installed instead of our Pale Moon fork of it.
    The crash has been pinpointed to our latest NSS library update.
    We are currently investigating the exact cause of this, and will be backing out the NSS update (as well as disabling TLS 1.3 draft support since the draft supported by the older NSS version is going to be obsolete very soon) to resolve the crashes in the next point release.
    Status: [Fixed] (long term solution is [In progress])
    Workaround: If you are a greasemonkey 1.15 user, please update to our Pale Moon fork of it.
    Timeline: Crash fixed in 27.8.1
27.7.0:
  1. Tab borders are drawn too thick when visual elements in Windows are scaled up
    At 125% or 150% scaling of visual elements in Display Options in Windows, the borders of tabs may be drawn thicker than intended in the default theme.
    This is a side-effect of the natural border size rounding introduced in Pale Moon 27.7.0 combined with non-standard styling of tabs in our UI. This needs some tweaking of our default theme.
    Status: [Fixed]
    Workaround: Can be adjusted with userChrome.css; please see our forum for details.
    Timeline: Fixed in 27.7.1
  2. Some websites have operational issues since 27.7.0
    This is caused by an incomplete implementation of the new "Unscopables" ES6 feature in JavaScript. Fixing this is our current priority.
    Status: [Fixed]
    Workaround: None. You may want to revert to 27.6.2 for the time being or switch to the "Unstable" versions where any fixes will land the moment they are done.
    Timeline: Fixed in 27.7.1

27.6.0:
  1. Pale Moon launches twice when opening a URL from the command-line/other program.
    This is a regression introduced in 27.6.0 due to an incorrect workaround for new window focus.
    Status: [Fixed]
    Workaround: None, but you can use the unstable version in the meantime if this is a breaking issue.
    Timeline: Fixed in v27.6.1
  2. Logging in to CitiBank's on-line banking fails.
    The server gives cryptic error message that the website it temporarily unavailable -- as it turns out this seems to be a user-agent sniffing issue which can easily be worked around (it's not a browser bug).
    Status: [Workaround]
    Workaround: in about:config, change the existing preference general.useragent.override.citi.com to "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:57.0) Gecko/20100101 Firefox/57.0 (Pale Moon)". When the default override for this site will be updated, you can reset the pref to use Pale Moon's default again (in case another change is needed in the future, and to accurately reflect dynamic parts of the override).
    Timeline: The override for this site will be updated in 27.6.1.

27.2, 27.3:
  1. Video playback on some sites is problematic
    On some sites, video playback is problematic. This is generally caused by Media Source Extensions being in use. While we are working on aligning this to the spec and behavior of other browsers, some sites may still cause issues, like refusal to play, video/audio de-sync, or other issues that prevent proper playback of video in the web browser.
    Status: [Fixed]
    Workaround: in Options -> Content, try disabling Media Source Extensions
    Timeline: Fixed for MP4 (default settings) in v27.4
27.1:
  1. Hangs may occur on media-heavy sites like Facebook and YouTube
    On some machine/operating system combinations, the browser may hang when using media-heavy sites like Facebook and YouTube. This is especially likely on those systems if you switch away from the site for a time, then return to the tab of the site. Forcefully closing the Pale Moon process may be the only way to recover.
    This is a rather complex bug in the media back-end (mostly because media playback is asynchronous and uses multiple threads).
    Potential workarounds: using a tab unloader extension like BarTab, disabling autoplay of videos, closing the tab when you're done with the site and reloading the site when you want to check it next.
    Status: [Fixed]
    Timeline: v27.2.0 has all but eliminated the offending code, and these deadlocks should no longer occur.
  2. 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.
27.0:
  1. Twitch.tv doesn't work
    Pale Moon 27.0.0 is unable to play twitch.tv 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
27.*:
  1. 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.
  2. 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.
26.*:
  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.


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