SeaMonkey 2.0

These release notes describe system requirements, installation instructions, and known issues for SeaMonkey 2.0. These notes are updated when we receive feedback, so please check back for new information.

What's New in SeaMonkey 2.0

SeaMonkey 2.0 contains the following major changes relative to SeaMonkey 1.1.18:

  • SeaMonkey uses the same internal platform as Firefox 3.5.4 now. Due to this change SeaMonkey is now much closer to Firefox as far as user profiles, add-ons and functionality of user interface elements are concerned.
  • The default location of user profiles has changed. Legacy profiles, e.g. from SeaMonkey 1.x, or even Thunderbird profiles, can be migrated automatically, excluding third-party add-ons (extensions and themes). The old profile will not be touched (instead, copies are made).
  • The new Add-on Manager allows to install, update, disable and remove extensions (add-ons), themes and plugins using the same mechanisms Firefox uses. This should ease extension management and development considerably.
  • Session restore (crash recovery) has been added. Now, when SeaMonkey crashes, all your browser windows and tabs will be restored automatically or on request (including data entered in web forms!). In addition, users can select to always restore the browser windows and tabs from their last open session when starting SeaMonkey.
  • Reopening closed browser windows (Undo Close Window) is now possible.
  • History is now stored in a better database solution, so that it can easily keep more information, and the location bar determines which addresses to autocomplete and/or show in the drop down menu with a smarter algorithm based on what you type, searching in both URL and title of visited pages by default.
  • Toolbars in the browser, main MailNews and message compose windows are now fully customizable, including icon size and whether to display icons and/or text for every major toolbar, all available via their context menus.
  • The MailNews component now includes support for reading RSS and Atom feeds. The browser detects feeds offered by web pages, can preview them and offers different ways to subscribe to them.
  • New IMAP accounts will now keep local offline copies by default, as a part of a number of speed improvements when working with IMAP. Synchronization can be disabled per account or for individual folders, and limited to the most recent messages in the Synchronization & Storage settings.
  • Tabbed Mail enables accounts, folders and even single messages to be opened in tabs inside the Mail & Newsgroups window. This feature also enables the Lightning extension to be installed into SeaMonkey for calendering functionality.
  • Password Manager was switched to an improved version, allowing easier searching, and notification bars replacing modal dialogs for remembering logins.
  • Download Manager has been completely reworked, including support for cross-session resumable downloads.
  • A new form manager replaces all previous web form management, and automatically keeps a record of what you type into forms and presents you these options in a drop-down list when you come back.
  • Cookie Manager has been improved and now allows searching for cookies by site and cookie name.
  • Gecko, the rendering engine used in SeaMonkey, has seen many improvements since the version used in the last stable release. Changes range from a better graphics backend (Cairo/Thebes) to improved support for fonts, CSS, DOM and JavaScript. SeaMonkey 2.0 passes the Acid2 test and most of Acid3 and includes all the HTML5 and other new web-facing features also included in Firefox 3.5, such as audio/video elements, downloadable fonts and JIT-compiled JavaScript.
  • Most of the icons in the default theme have been exchanged for newer images that fit better with the look of modern desktop environments.
  • The default theme on Mac OS X was completely renewed to better fit with the look of Leopard and Snow Leopard.
  • For extension developers, SMILE is introduced, making interfaces known from FUEL and STEEL also available in SeaMonkey.
  • Support for Windows 95, 98, Me and NT 4 was dropped. GTK 2.10 or higher is now required on Linux/UNIX. Support for Mac OS X 10.3 ("Panther") and 10.2 ("Jaguar") was also dropped.

The changes page lists more details on those new features and fixes relative to SeaMonkey 1.1.18.


The SeaMonkey project provides official versions of SeaMonkey 2.0 for Windows, Linux, and Mac OS X in US English and other languages. Community volunteers are also contributing builds for other platforms. You can download SeaMonkey 2.0 here.

System Requirements, Installation and Uninstallation

Before installing, make sure your computer meets the system requirements. SeaMonkey 2.0 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 2.0 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 2.0. Please read this before reporting any new bugs.
  • Installing SeaMonkey 2.0 into the same location where an older version of SeaMonkey is installed will result in a non-working installation. Either install SeaMonkey 2.0 to a different location - for example the default installation location as given by the installer - or un-install the older version of SeaMonkey first. (Bug 526202)
  • Clearing private data can stop password manager from working (including password lists appearing empty) until the next restart of SeaMonkey (Bug 523345)
  • Only one profile from SeaMonkey 1.x is migrated to SeaMonkey 2.0 automatically (Bug 383006)
    Workaround: Manually start migration as described in the knowledge base.
  • Migrating a SeaMonkey 1.x profile may set "Use secure authentication" in the Outgoing Server (SMTP) settings, which causes an error when trying to send to a server supporting GSSAPI (Kerberos authentication) if it is not configured on the client machine. Unchecking that option resolves the issue. (Bug 522633)
  • New email count on the Mac OS X dock icon is sometimes wrong (Bug 509163)
  • MailNews account password prompts are no longer serial at startup (Bug 338549)
    Workaround: If a Master Password is set and you saved your login credentials, only one prompt will appear at startup. You can disable this new behavior by setting signon.startup.prompt to false in about:config.
  • For some Windows users, cutting or copying text, links, whatever from anywhere in SM 2.0 does not appear to place the cut or copied text in the Clipboard. Some reports say that "McAfee SiteAdviser Service" might be responsible and completely deleting or shutting down this service might fix the problem. (Bug 525601)
  • Profile Roaming is not working any more (Bug 378647)
  • "Turbo mode" (quick launch), including the tray icon, has been removed (Bug 361682)
  • Splash screen support (was shown by default on Windows) has been removed due to not being implemented in the new toolkit (Bug 329742)
  • Download manager sometimes uses high amounts of CPU time with multiple downloads active or in the list (Bug 506731)


  • 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 2.0 source code?
A tarball of the SeaMonkey 2.0 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 2.0: