SeaMonkey 2.1

These release notes describe system requirements, installation instructions, and known issues for SeaMonkey 2.1. These notes are updated when we receive feedback, so please check back for new information.

What's New in SeaMonkey 2.1

SeaMonkey 2.1 contains the following major changes relative to SeaMonkey 2.0.14:

  • Sync (f.k.a. Weave) is now included directly in SeaMonkey. Sync allows you to keep your browsing history, passwords, bookmarks, preferences and tabs in sync across different devices (computers) in a secure way.
  • SeaMonkey windows can now be themed with Personas (lightweight themes).
  • The bookmarks system has been reworked to use the Places framework shared with Firefox (already used for history data in SeaMonkey 2.0), including a new Bookmark Manager and fast bookmarking button in the location bar.
  • Find in Page now works with a toolbar instead of a modal window.
  • OpenSearch plugins are now supported and the default for web search.
  • An optional search bar (including suggestions if the search engine supports it) is available in browser toolbar customization, and an engine manager for OpenSearch is available.
  • More toolbar widgets are now customizable.
  • The new Add-ons Manager opens directly in the browser now and has received a major facelift.
  • The new Data Manager now unifies cookie, permission, password, and form data management.
  • Flash cookies (LSOs) will now be removed when using Clear Private Data / Cookies (requires Flash Player 10.3 or better).
  • Plugin crashes do not take down the whole application anymore since plugins run in their own processes now.
  • Plugins now work in feeds shown in MailNews windows.
  • The feed preview UI and the Helper Applications preferences can now detect the system's default feed reader and use it.
  • Page zoom is being remembered on a site-specific basis now.
  • The browser tab bar is now scrollable to cope with tab overflow. This includes an "All Tabs" navigation button to quickly list all open tabs.
  • You can now drag and drop downloads, e.g. from the Download Manager to the desktop.
  • SeaMonkey now shows "doorhangers" for notifications like remembering log-in passwords or after installing an extension.
  • The new DoNotTrack HTTP header is supported (configurable in Preferences).
  • A page with Troubleshooting Information (about:support) and the option to restart in Safe Mode are now available from the Help menu.
  • Loading the URL about:memory now shows how much memory is used by different parts of SeaMonkey.
  • SeaMonkey should now support more websites that previously appeared to only work with Firefox (configurable in Preferences).
  • Built-in extensions (ChatZilla, JavaScript Debugger and DOM Inspector) are now installed into the profile.
  • News messages can now be deleted from local storage.
  • Cascaded Session Restore improves restoring large browsing sessions.
  • SeaMonkey now uses Omnijar which results in fewer installed files, less fragmentation and better startup time.

Platform-specific changes

  • Mac OS X 10.4 "Tiger" and PPC support was dropped, 64-bit support for 10.6 "Snow Leopard" was added.
  • On Linux, desktop notifications (e.g. mail alerts, finished downloads) show up in the native environment.
  • Windows 7 Jump Lists support was added.
  • Download progress is now shown in the Windows 7 taskbar.

Mozilla platform changes

  • Better performance on startup and shutdown, and memory usage improvements.
  • Protection from out-of-date plugins has been added.
  • Text areas in web forms are now resizable.
  • CSS :visited selectors have been changed to block ways that websites can quickly check a user's browsing history.
  • The WOFF format for downloadable website fonts is now supported.
  • SMIL animation in SVG is now supported.
  • New CSS attributes such as gradients, background sizing, and pointer events have been implemented.
  • A new HTML5 parser is used for all HTML documents.
  • New DOM and HTML5 features including the Drag & Drop API and the File API are now supported.
  • JS-ctypes support has been improved, allowing in-application JavaScript code to access native system libraries.
  • HTML5 video can now be viewed full screen and supports both the WebM format and the "buffered" property.
  • Web developers can animate content using CSS Transitions.
  • The W3C Indexed Database API is now available to websites.
  • JavaScript is faster than ever with the new JägerMonkey engine.
  • Support for WebGL, Direct2D and Direct3D acceleration on Windows has been added (see about:support for support and Preferences for configuration).
  • The HSTS security protocol and the proposed Audio Data API are available.
  • OpenType support has been improved.
  • HTML5 Forms API support has been added.

The changes page lists a more detailed overview of new features and fixes relative to our last stable release, SeaMonkey 2.0.14. Relevant security fixes are listed on Security Advisories for Firefox 3.6 and Security Advisories for Firefox 4.


The SeaMonkey project provides official versions of SeaMonkey 2.1 for Windows, Linux, and Mac OS X in US English and experimental language packs for a small variety of other languages. Community volunteers are also contributing builds for other platforms. You can download SeaMonkey 2.1 here.

System Requirements, Installation and Uninstallation

Before installing, make sure your computer meets the system requirements. SeaMonkey 2.1 will offer to migrate your data from SeaMonkey 1.x or Mozilla 1.x at the first start after installation. You can find more details about installation, profile data and uninstallation in our install and uninstall document.

Extensions and Themes

Extensions installed under SeaMonkey 1.x are not migrated to SeaMonkey 2, and may not be compatible for reinstalling in this version due to major changes in our architecture. Please report any issues to the maintainer of the extension. Extensions and Themes for SeaMonkey 2.1 can be installed from the SeaMonkey Add-Ons website or the "Get Add-Ons" section in the Add-ons Manager.

Known Issues

This list covers some of the known problems with SeaMonkey 2.1. Please read this before reporting any new bugs.
  • Data loss warning: If you use a profile with this or any later version and then try to go back to SeaMonkey 2.0, SeaMonkey will rename your history file to places.sqlite.corrupt and create a new places.sqlite file, effectively resetting your browsing history. This is because the internal format changed and the upgrade process only works in one direction.
  • If you are using SeaMonkey with one of the following locales, Help will be broken. We hope to fix this for the next release. The locales are: en-GB (British English), es-AR (Argentine Spanish), pt-PT (Portuguese), and tr (Turkish).
  • In some cases where an old profile has been migrated, the sound settings (Browse, Play) on the Popup Windows Preferences pane do not work. Try resetting the privacy.popups.sound_url pref from about:config (bug 658060).
  • After creating a news account through clicking a news URL, the MailNews account wizard may be broken (the account type will always be News). To work around the problem, set the mail.server.serverX.valid pref (where X is the internal number of the corresponding news account) to true in about:config, or delete the invalid news account (bug 521861).
  • Opening messages from Advanced Search results does not work anymore (bug 660882). This issue will be fixed for the next release. Until then, use Open Message Folder as a workaround.
  • The Archives folder is rendered inaccessible after archiving a news posting (bug 660845). This issue will be fixed for the next release (at least by default). For now, avoid archiving news postings and restart the application if this happened to you.
  • Trying to open a message attached to another message will show garbage in the browser instead of opening a message window. Workaround: append "&type=message/rfc822" to the URL opened in the browser (bug 665313).
  • Select Element by Click doesn't flash the element in DOM Inspector on Windows (bug 594299).
  • On the first wizard page for creating a new Sync account, the Next button is disabled until you switch the server type and back (bug 664569). This issue will be fixed for the next release.
  • To use a Sync account with multiple devices you need to make sure all of them use the latest version of Sync (e.g. SeaMonkey 2.1 in combination with Firefox 4, desktop and mobile) (bug 615950).
  • The option "When opening a bookmark group" / "Replace existing tabs" under Preferences / Tabbed Browsing does not have an effect anymore (bug 664101).
  • Lightning options cannot be opened from the Add-ons Manager. Instead, Lightning preferences can be accessed from Preferences/Lightning (bug 636104).
  • Lightning keyboard shortcuts for accessing the calendar tab from within the MailNews window or from the main menu (Ctrl+Shift+C/D) do not work. (bug 514512).
  • Composer removes link information when pasting a link to a local file or anchor (bug 647682).
  • After installing Firebug 1.7.x and restarting the application, the Navigation Toolbar may be broken (bug 658444), and opening Firebug in its own window will break it for the rest of the session. Both issues have been fixed in Firebug 1.8.0a3.
  • Windows 7:
    • Downloads to network shares may be corrupted (bug 545650). This issue will be fixed for the next release.
  • Mac:
    • When hardware acceleration is off, background colors in the UI (toolbar, status bar etc.) might not update correctly when you switch focus from/to a window. Users running Macs with certain older hardware (e.g. Intel GMA 950) will experience this even if they haven't turned off hardware acceleration in Preferences (Appearance/Content) (bug 626096).
  • Linux:
    • The video control buttons may not work when viewing QuickTime videos with libtotem (bug 625036).
    • Users compiling from source might need a newer gcc and libstdc++ as the build requirements have changed (bug 578880).


  • Some questions are asked more frequently than others. Have a look at the SeaMonkey FAQ. Maybe your particular problem has already been solved.
  • Some anti-virus software keeps detecting our installers as containing a "Trojan" or "Downloader". This is a false positive and is some wrong detection mechanism in the anti-virus software. The code in question is actually from 7-Zip and decompresses the installer so that its contents can run and install SeaMonkey. That technology is widely used and probably can be used to compress bad as well as good software, but the 7-Zip code itself is perfectly safe. Mozilla scans all our files routinely when putting them on the FTP server and we assure you that our installers are as clean as the official Firefox downloads that are scanned by the same mechanisms.
  • Poorly designed or incompatible extensions can cause problems with SeaMonkey, including make it crash, slow down page display, etc. If you encounter strange problems relating to parts of SeaMonkey no longer working, the browser not starting, windows with strange or distorted appearance, degraded performance, etc, you may be suffering from Extension or Theme trouble. Restart SeaMonkey in Safe Mode. On Windows, start using the "Safe Mode" shortcut created in your Start menu or by running seamonkey.exe -safe-mode. On Linux, start with ./seamonkey -safe-mode and on Mac OS X, run:

    cd /Applications/
    ./seamonkey-bin -safe-mode

    When started in Safe Mode all extensions are disabled and the Default theme is used. Disable the Extension/Theme that is causing trouble and then start normally.
  • If you uninstall an extension that is installed with your user profile (i.e. you installed it from a Web page) and then wish to install it for all user profiles using the -install-global-extension command line flag, you must restart SeaMonkey once to cleanse the profile extensions datasource of traces of that extension before installing with the switch. If you do not do this you may end up with a jammed entry in the Extensions list and will be unable to install the extension globally.
  • If you encounter strange problems relating to bookmarks, downloads, window placement, toolbars, history, or other settings, it is recommended that you try creating a new profile and attempting to reproduce the problem before filing bugs. Create a new profile by running SeaMonkey with the -P command line argument, choose the "Manage Profiles" button and then choose "Create Profile...". Migrate your settings files (Bookmarks, Saved Passwords, etc) over one by one, checking each time to see if the problems resurface. If you do find a particular profile data file is causing a problem, file a bug and attach the file.

Frequently Asked Questions

What can I do to help?
We need help from developers and the testing community to provide as much feedback as possible to make SeaMonkey even better. Please read these notes and the bug filing instructions before reporting any bugs to Bugzilla. You can also give us your feedback through this feedback form.
Why haven't you responded to the mail I sent you?
Use the newsgroup. The SeaMonkey team reads it regularly, and your email may have gotten lost.
Where can I get extensions and themes (add-ons)?
Extensions and Themes can be downloaded from SeaMonkey Add-ons.
Who makes SeaMonkey?
Lots of people. See Help->About SeaMonkey, contributors for a list of some of the people who have contributed to Mozilla and SeaMonkey.
Where's the SeaMonkey 2.1 source code?
A tarball of the SeaMonkey 2.1 source code is available at the download page. The latest development code can be obtained from the source repository. SeaMonkey-specific source is in the "suite" directory. Please follow the build instructions.

Other Resources and Links

The following resources contain useful information about SeaMonkey 2.1: