The new major release of the all-in-one Internet suite is available for download now. Building on the same Mozilla platform as the newest Firefox release, it delivers the latest developments in web technologies such as HTML5, hardware acceleration and improved JavaScript speed.

f you are using macOS 15.1.x please update to 15.2. Because of a bug in the OS SeaMonkey can not be started via Finder or Dock without workarounds. This applies to older versions too.

SeaMonkey is available in 23 languages, for Windows, macOS x64 and Linux.

Features

Browser

  • Tabbed browsing gives you a better way to surf the net. You no longer have to open one page at a time. With tabbed browsing, open several pages at once with one click. Plus, your homepage can be multiple pages, in tabs. And if you mistakenly close a tab or window, functionality to Undo Closed Tab or Window helps you bring it back to continue working with it.
  • Session restore brings back all your open windows and tabs after the rare occasion that SeaMonkey crashes – and if you wish even when you close and reopen the browser or restart your computer. However, crashes should be rare nowadays because crashing plug-ins will no longer take the whole application down.
  • SeaMonkey's powerful Add-ons Management provides almost infinite possibilities to extend your Internet experience both through installing additional functionality created by others and even freely developing your own extensions and providing them to the rest of the SeaMonkey community.
  • SeaMonkey's unique Data Manager serves as a central management interface for all kinds of site-specific data, including cookies, permissions (e.g. image blocking), preferences, passwords and form data.
  • Lightweight themes (Personas) let you give your SeaMonkey a personal touch through simple theming. You can choose from thousands of Themes!
  • Feed detection notifies you when web pages offer RSS or Atom feeds, and feed preview lets you view their contents and choose a reader with which to subscribe to those – including an internal reader in the Mail & Newsgroups component of SeaMonkey.
  • Smart Location Bar enables you to search your visited web pages as you type into the browser's location bar and find what you want to re-visit as quickly as possible by learning which pages you visit frequently.
  • Popup blocker lets you surf the web without interruption from annoying ads.
  • Find as you type gives you another way to navigate a page. Just start typing to jump from link to link or to find a word or phrase within a page.
  • Safe Mode can help you solve problems that might occur, e.g. with incompatible add-ons. If you need to ask someone for support, the Troubleshooting Information page provides quick access to basic technical information.
  • Plus all the features a modern browser should have, including: Advanced security settings, download management, web form autocompletion, themes, toolbar customization, multi-language and multi-platform support, plus support for the latest web standards.

Mail & Newsgroups

  • Tabbed Mail lets you manage your mail and folders in parallel, without losing control of where you're at when reading, replying to and working with messages in more complex patterns.
  • Junk mail controls help you take back control of your e-mail from spammers. SeaMonkey's adaptive junk mail control gets smarter with use and is personalized to the e-mail that you receive.
  • Manage your mail with customizable Tags and Mail Views. Color code your e-mail to help you prioritize. Filter your mail with views to help you sort through your e-mail much faster.
  • Multiple accounts support helps you manage all your mail through one interface.
  • Blogs & News Feeds is a reader for RSS and Atom feeds right in your messaging center that eases your reading of information from all across the web.
  • SeaMonkey Mail & Newsgroups includes enterprise-ready features such as S/MIME, return receipts, address books, LDAP support, and digital signing.

Composer

  • SeaMonkey's powerful yet simple HTML editor keeps getting better with dynamic image and table resizing, quick insert and delete of table cells, improved CSS support, and support for positioned layers. For all your documents and website projects, Composer is all you need.

IRC Chat ("ChatZilla")

  • Chat on IRC networks with this simple yet powerful IRC client. Multiple networks and channels are easy to keep track of in a familiar tabbed interface.
  • You can change the look and feel of the chat with motifs; choose from several built-in motifs, many more downloadable, or create your own with CSS.

Web Development Tools

  • DOM Inspector enables you to dig into the document structure of web pages, add-ons or even the SeaMonkey "chrome" itself and inspect a huge number of properties of any element in that structure, including JavaScript objects and CSS styles.
  • JavaScript Debugger ("Venkman") lets you debug JavaScript code on your websites, add-ons and even in SeaMonkey itself with a suite of powerful debugging tools.

What's New

SeaMonkey 2.53.21 contains (among other changes) the following changes relative to SeaMonkey 2.53.20:

  • Unable to load JSON Bookmarks file, Open/Cancel do the same thing bug 1940204.
  • Move replaceVars helper into menu-manager.js for cZ bug 1937379.
  • Remove dumpObject helper from utils.js in cZ bug 1937380.
  • Remove toOpenWindowByType helper from utils.js in cZ bug 1937382.
  • Fix makeLogName helper to not encode twice in prefs.js in cZ bug 1937387.
  • Remove use of escapeFileName helper and tidy up pref_mungeName helper in cZ bug 1937395.
  • Add helper to file-utils.js for ensuring an nsIFile is returned in cZ bug 1937397.
  • Remove unused http.js file from cZ bug 1937890.
  • Remove unused IRC tests from static.js in cZ bug 1937896.
  • Switch from deprecated escape/unescape in cZ bug 1938933.
  • Tidy up use of prefBranch outside of pref-manager in cZ bug 1938935.
  • Make use of pref fallbacks in pref-manager in cZ bug 1938937.
  • Remove unused edit context menu from cZ bug 1939929.
  • Use XPCOMUtils.generateQI in connection-xpcom in cZ bug 1939930.
  • Merge menus.xul, popups.xul and scripts.xul into chatzilla.xul bug 1939958.
  • Make use of toSOutputStream and toSInputStream helpers in DCC code in cZ bug 1939965.
  • Stop hard-coding commandkey for reloadui in cZ bug 1939968.
  • Use suite's FillInHTMLTooltip helper instead of having own version in cZ bug 1939969.
  • Split custom-away from other away/back commands in cZ bug 1942655.
  • Remove ChatZilla Homepage link from Help menu and about command in cZ bug 1942916.
  • Re-arrange toolbar menus in cZ bug 1943783.
  • Remove ChatZilla Homepage link from about and prefs dialogs in cZ bug 1943844.
  • Use custom controller for userlist and tidy up some controller use in cZ bug 1945325.
  • Make use of observes for show/hide elements in cZ bug 1945378.
  • Don't dynamically create focus-input key element in cZ bug 1947028.
  • Remove unused toolbar creation code in cZ bug 1947030.
  • Remove unused updateMenus code from cZ bug 1947031.
  • Clean up whitespaces in cZ package manifest bug 1947040.
  • Remove unused uninstallKeys code from cZ bug 1950002.
  • Use node.remove(), especially instead of node.parentNode.removeChild(node) in cZ bug 1951250.
  • Remove __cz_condition from cZ bug 1951253.
  • Remove outputWindowURL pref from cZ bug 1951256.
  • Remove unused JS tests in cZ bug 1951297.
  • Use includes, startsWith and endsWith instead of indexOf and substr in cZ bug 1951302.
  • Use {} and [] instead of new Object() and new Array() in cZ bug 1951303.
  • Fixup function naming for lint in cZ bug 1955141.
  • Fixup method naming for lint in cZ bug 1955767.
  • Remove old Mozilla 1.0 code from updateAppMotif in cZ bug 1955771.
  • Use throw Components.Exception in cZ bug 1955774.
  • Migrate output-window from HTML to XHTML to make localisation more standard in cZ bug 1955825.
  • Merge munger.js into mungers.js in cZ bug 1956373.
  • Remove unused tagName from mungers.js in cZ bug 1956374.
  • Flatten directory structure in cZ bug 1956375.
  • Tidy up about dialog page in cZ bug 1956376.
  • Add helper to commands.js for sending CTCP commands in cZ bug 1956377.
  • Migrate to standard menus for menu toolbar in cZ bug 1957763.
  • Install plugin dialog broken in cZ bug 1961599.
  • cZ change nick menu not working bug 1962112.
  • Away status isn't reflected correctly in all channels in cZ bug 1962234.
  • Fix dark motif userlist in cZ bug 1967072.
  • SeaMonkey Composer adds moz-do-not-send attribute for links and images bug 1827146.
  • Use menu_Toolbars overlay for navigatorOverlay and console bug 1945335.
  • Remove defunct 2.53 prerelease builds from debugQA extension bug 1947043.
  • Handling of MOZ_LANGPACK_CONTRIBUTORS in defines.inc files should be less custom bug 1951101.
  • Control + U shortcut for underlined text is not working bug 1872514.
  • Context menu search (with default search engine) does not work in the content area of a message compose or SM-Composer window bug 1062092.

The following bugs were fixed in our branch of the Gecko source code only:

  • on FreeBSD sqlite3 fails to link for missing math functions bug 1944954.
  • Expand init.configure to use version_package.txt to set MOZ_PKG_VERSION bug 1952757.
  • Change supported msvc Compilers for SeaMonkey 2.53 bug 1954176.

SeaMonkey 2.53.21 contains (among other changes) the following major changes relative to SeaMonkey 2.49.5:

  • The Bookmarks Manager has switched its name to Library, and now also includes the History list. When History is invoked, the Library will be shown with the History list selected. The extensive modifications were needed because of Mozilla Gecko platform API changes.
  • Download Manager has been migrated to a new API. Although it looks pretty much the same as before, the search option is missing and some other minor details work differently. The previous downloads history is removed during the upgrade.
  • The layout panel was added to the CSS Grid tools.
  • TLS 1.3 is the default SSL version now.
  • Support for all NPAPI plugins like Flash, Java and Silverlight has been removed. For displaying pdf files in the browser you can use pdf.js-seamonkey from Isaac Schemm.
  • SeaMonkey now uses a new api for formatting regional data like time and date. Default is to use the application locale of the current SeaMonkey build. If you use a language pack or a different OS formatting this is usually not desired. You can change the formatting from the application locale to the regional settings locale (OS) in the preferences dialog under "Appearance".