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. Vimeo videos may not play
    The way Vimeo uses MSE for a good percentage of their videos (either on their main site or embedded in other sites) prevents Pale Moon from playing them (videos will not start).
    We are still working on improving MSE and its integration with the media components to address this. because of the complexity of the media components this will take time.
    Status: [In Progress]
    Workaround: Go into Options -> Content, and uncheck "Enable MSE for MP4 video". Note that this workaround may prevent other sites from displaying video.
  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. 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.
  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.

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