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The SeaMonkey^® Project

The SeaMonkey project is a community effort to develop the SeaMonkey Internet Application Suite (see below). Such a software suite was previously made popular by Netscape and Mozilla, and the SeaMonkey project continues to develop and deliver high-quality updates to this concept. Containing an Internet browser, email & newsgroup client with an included web feed reader, HTML editor, IRC chat and web development tools, SeaMonkey is sure to appeal to advanced users, web developers and corporate users.

Under the hood, SeaMonkey uses much of the same Mozilla Firefox source code which powers such products as Thunderbird. Legal backing is provided by the SeaMonkey Association (SeaMonkey e.V.).

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Project News

December 31, 2025

SeaMonkey 2.53.23 released

The SeaMonkey project is proud to present SeaMonkey 2.53.23: The new release of the all-in-one Internet suite is available for free download now!

2.53.23 is an incremental update on the 2.53.x branch and incorporates a number of enhancements, changes and fixes to the application as well as those from the underlying platform code. We have also added many fixes and backports for overall platform stability.

Please be advised that 2.53.21 was the last release with 32-bit versions for Windows and Linux, this version is only 64-bit.

Support for PostMessageOptions for MessagePort has been added to fix issues with the new version of RECAPTCHA.

Support for CSS justify-items legacy has been added to Gecko.

A Linux crash on close issue has been fixed.

If 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.

We are aware of numerous websites breaking because of only supporting the latest Chrome or Firefox versions. We are trying to address this and progress has been made in a different source code branch but the code is not ready for general distribution yet.

SeaMonkey 2.53.23 is available in 24 languages, for Windows x64, macOS x64 and Linux x64.

Automatic upgrades from previous 2.53.x versions are enabled for this release, but if you have problems with it please download the full installer from the downloads section and install SeaMonkey 2.53.23 manually over the previous version.

For a more complete list of major changes in SeaMonkey 2.53.23, see the What's New in SeaMonkey 2.53.23 section of the Release Notes, which also contains a list of known issues and answers to frequently asked questions. For a more general overview of the SeaMonkey project (and screen shots!), visit www.seamonkey-project.org.

We encourage users to get involved in discussing and reporting problems as well as further improving the product.

January 12, 2025

January 6th, 2025 was a sad day for SeaMonkey and all of us

Our friend, SeaMonkey developer and releng William Andrew Gianopoulos, better known as WG9s, passed away unexpectedly on Monday, January 6, 2025.

Visit his obituary for further details and, if you feel so, add a condolence message.

We are still all very sad and will miss him and his cat Bella much. Light a candle for him and remember: No one is really dead unless you stop thinking about him or her and we won't forget him and what he did for sure.

He left a big hole and we will see what we can do about publishing prerelease builds in the future.

Rest in Peace Bill

November 6, 2022

SeaMonkey and macOS Ventura

Attention macOS users! The current SeaMonkey release crashes during startup after upgrading to macOS 13 Ventura. Until we have a fix we advise you not to upgrade your macOS installation to Ventura. No usable crash information is generated and this might take a bit longer than usual to fix. This is not a problem with Monterey 12.6.1 or any lower supported macOS version so might even be an Apple bug.

The problem is tracked in Bug 1797696.

The SeaMonkey Internet Application Suite

SeaMonkey has inherited the successful all-in-one concept of the original Netscape Communicator and continues that product line based on the modern, cross-platform architecture provided by the Mozilla project.

• The Internet browser at the core of the SeaMonkey Internet Application Suite uses the same rendering engine and application platform as Mozilla Firefox, with popular features like tabbed browsing, feed detection, popup blocking, smart location bar, find as you type and a lot of other functionality for a smooth web experience.
• SeaMonkey's Mail and Newsgroups client shares lots of code with Thunderbird and features adaptive Junk mail filtering, tags and mail views, web feeds reading, tabbed messaging, multiple accounts, S/MIME, address books with LDAP support and is ready for both private and corporate use.
• Additional components include an easy-to-use HTML Editor, the ChatZilla IRC chat application and web development tools like a DOM Inspector.
• If that's still not enough, SeaMonkey can be extended with numerous Add-Ons that provide additional functionality and customization for a complete Internet experience.