SeaMonkey 2.6.1 contains the following major changes relative to SeaMonkey 2.5:

SeaMonkey-specific changes

• Added support for the HTML5 "context menu" feature (contextmenu attribute)
• Added Print Preview support to Composer
• Added update channel indication to About SeaMonkey page (about:)

Mozilla platform changes

• Added Type Inference, significantly improving JavaScript performance
• Added support for querying Do Not Track status via JavaScript
• Added support for font-stretch
• Improved support for text-overflow
• Improved standards support for HTML5, MathML, and CSS
• Fixed several stability issues

The changes page lists a more detailed overview of new features and fixes relative to our last stable release, SeaMonkey 2.5. Relevant security fixes are listed on Security Advisories for SeaMonkey.

The SeaMonkey project provides official versions of SeaMonkey 2.6.1 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 2.6.1 here.

Before installing, make sure your computer meets the system requirements. SeaMonkey 2.6.1 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 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 2.6.1 can be installed from the SeaMonkey Add-Ons website or the "Get Add-Ons" section in the Add-ons Manager.
If you want to check whether your most important add-ons are already compatible with the SeaMonkey version to be installed, please refer to the SeaMonkey Add-ons Compatibility Tracking wiki page for an overview.

Extensions with binary components such as Lightning, Enigmail and HTML Validator only work on certain platforms (e.g. Windows). Furthermore they need to be adjusted for each new SeaMonkey release, which also means that an old version of such an add-on can break SeaMonkey if you disabled compatibility checking (which e.g. happens when you install the Add-on Compatibility Reporter add-on).
Lightning provides versions compatible with the latest SeaMonkey beta through its Development Channel which has an own section at the bottom of the Lightning add-on page. Other Lightning releases can be found on the Calendar Versions page.
For Enigmail, please refer to the Enigmail Nightly Builds page.
For HTML Validator you need to check whether the Firefox version that appears on SeaMonkey's about: page is listed on the 0.9x download page. Note that only Windows is supported at this time.

This list covers some of the known problems with SeaMonkey 2.6.1. 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.
• Under certain conditions, entire newsgroups are marked as unread and authentication data (user name and password) is lost (bug 695309). This issue will hopefully be fixed in SeaMonkey 2.7 final.
• The Recently Closed Tabs/Windows menu items have been moved from the File menu to the Go menu (bug 599731), but the menu items do not get disabled anymore in case nothing can be restored (bug 702297).
• If you had added the print button to the MailNews window toolbar, you now need to add it back manually once again using the Customize Toolbar functionality (bug 745176).
• Attachments in emails with certain structures or encodings may not be shown in the attachment pane. Set the mailnews.display.show_all_body_parts_menu pref to true in about:config, then select View/Message Body As/All Body Parts to make such attachments available (bug 677905).
• Bookmarklets (JavaScript bookmarks) that move or resize the window do not work anymore bug 688841). As a workaround, use add-ons like Custom Buttons or Prefbar.
• 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).
• Web pages may appear differently in the MailNews feed reader than in the browser (bug 662907). Workaround: Add a "noscript {display:none}" rule to your userContent.css (note that the Stylish add-on cannot be used here since it does not integrate with the MailNews feed reader).
• Select Element by Click doesn't flash the element in DOM Inspector on Windows if hardware acceleration is enabled (bug 594299).
• 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).
• If you try to start SeaMonkey using a locked profile, it will crash (see bug 573369).
• For some users, visiting Google+ will cause the back and forward buttons to no longer work (see bug 670318).
• For some users, scrolling in the main GMail window will be slower than usual (see bug 579260).
• 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).

• 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.app/Contents/MacOS/
./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.

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 2.6.1 source code?

A tarball of the SeaMonkey 2.6.1 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.

The following resources contain useful information about SeaMonkey 2.6.1:

• SeaMonkey Documentation & Help
• MozillaZine Knowledge Base
• "SeaMonkey/Features/2.6" wiki page
• For extension developers