What big things do SeaMonkey 2.1 builds offer (over SeaMonkey 2.0)?
- News filters can now be applied after the fact (bug 178870).
- Support for the -search command line option (bug 648781).
- Safe Mode dialog (bug 573538).
- New Help menu entry to restart the application, optionally with add-ons disabled (bug 574612).
- Crashed plugins UI (bug 601493).
- Easy Setup for Sync (using J-PAKE) (bug 634419).
- Windows 7 Jump Lists support (bug 581526).
- Outdated plugins detection (bug 521159).
- Tabs can be switched using mouse scrolling (again, in addition to scrolling the tab bar) (bug 643294).
- WebGL support via ANGLE (bug 632148).
- 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 (bug 401417).
- The delete action in the MailNews Advanced Search dialog has been fixed (bug 594090).
- Plugins now work in feeds shown in MailNews windows (bug 615675).
- ChatZilla is working again (bug 605001).
- Download progress is now shown in the Windows 7 taskbar (bug 631796).
- Cascaded Session Restore (bug 597584).
- Remove Flash cookies (LSOs) when Cookies is selected in Clear Private Data (requires Flash Player 10.3) (bug 632746).
- Data Manager is opened instead of the previous separate management windows (bug 588419).
- Page zoom is being remembered on a site-specific basis now (bug 386363).
- WebSockets have been disabled for security reasons (bug 616733).
- Lightweight themes (Personas) support for the Address Book (bug 608966), Composer (bug 579739), and MailNews (bug 579738) windows.
- Deferred Session Restore (bug 614220).
- The browser tab bar is now scrollable (also using the mouse wheel) to cope with tab overflow. Includes an "All Tabs" navigation button to quickly list all open tabs (bug 484968).
- News messages can now be deleted from local storage (bug 250141).
- Website search fields now feature a "Add a Keyword for this Search" context menu entry (bug 332538).
- In some places where previously a notification bar appeared (like remembering log-in passwords or after installing an extension), SeaMonkey now shows a "doorhanger" below the location bar (bug 570004).
- SeaMonkey now uses Omnijar which results in fewer installed files, less fragmentation and better startup time (bug 588067).
- Sync (f.k.a. Weave) is now included directly in SeaMonkey (bug 576970).
- Mac changes: PPC support was dropped, 64-bit support for 10.6 "Snow Leopard" was added (bug 599862).
- The new DoNotTrack HTTP header can be configured in Preferences, Privacy & Security (bug 630270).
- WebGL and D3D are now enabled where supported (hardware acceleration, see about:support)
- Improved OpenType support
- HTML5 Forms API support
- Various Add-on Manager improvements
- Faster bookmarking and startup performance (due to Places changes)
- Flash on Mac OS X improvements
- Memory usage improvements
- OpenSearch plugins are now supported and the default for web search. (bug 410613)
- Data Manager now unifies cookie, permission, password, and form data management. (bug 569341)
- Plugins now run in their own processes and don't take down the browser any more if they crash. (bug 545716)
- The context menu of the location bar now has a "Paste and Go" option. (bug 599833)
- The location bar now features a fast bookmarking button. (bug 589601)
- SeaMonkey now builds most of the application into a single library ("libxul"). (bug 394502)
- Direct2D Hardware Acceleration is now on by default for Windows 7 users, hardware accelerated layers are available on all platforms with known-to-work video drivers.
- XUL in web pages is not allowed any more. (bug 546857)
- Reporter (Report a Broken Website) has been removed. (bug 590102)
- The proposed Audio Data API is available.
- The HSTS security protocol is available
- Absolute length units in CSS are not physical, but relative to CSS pixels now (on the basis of 96dpi). (bug 537890).
- The bookmarks system has been reworked to use the Places framework shared with Firefox (bug 498596), which will allow enabling Bookmarks with the Sync add-on (bug 585845).
- Several methods of the Firefox TabBrowser API (bug 558614, bug 558673, bug 579845) were implemented in SeaMonkey, which will allow to enable Tabs with the Sync add-on (bug 567583).
- The tab bar received a visual refresh. (bug 579732)
- Gopher support has been removed. (bug 572389)
- Web developers can animate content using CSS Transitions.
- SeaMonkey now defaults to tabbed browsing instead of opening new windows. (bug 505311)
- Address book toolbars can now be customized. (bug 575956)
- Find in Page now works with a toolbar instead of a modal window. (bug 97023)
- The browser can now be themed with Personas (lightweight themes). (bug 563261)
- The upcoming Gecko release has been renamed from 1.9.3 to 2.0. (bug 570022)
- The User-Agent (UA) string now exposes less information. (bug 572668: Crypto token, bug 572656: UI language, bug 581783: "Windows;")
- The Add-on Manager now shows add-on Preferences buttons (bug 562890) and versions (bug 562052) directly in the list and searches AMO now (bug 558287).
- SeaMonkey now supports the HTML5 video "buffered" property.* XPCOM registration has been changed. (bug 568691)
- Archiving can now keep the folder structure intact (no configuration UI yet). (bug 573392)
- The W3C Indexed Database API is now available to websites. (bug 553412)
- New Add-ons manager (bug 561600)
- Drag URL/file to/from SeaMonkey's Download Manager (copy/move to desktop/folder) (bug 192728)
- Save multiple messages as individual files in directory (bug 555972)
- Make Search, Folder Location and Views widgets for MailNews customizable toolbars (bug 521927)
- WebM video is now supported for HTML5 <video> tag. (bug 566245)
- View source is now consistently taken from the platform and appearing in a SeaMonkey look and feel across all invocations. (bug 411754)
- Loading the URL
about:memorynow shows how much memory is used by different parts of SeaMonkey.
- SeaMonkey now supports a lot of the same tabbrowser API as Firefox. (bug 467867)
- Search and Go buttons widgets for Browser are now customizable. (bug 529647)
- The feed preview UI and the Helper Applications preferences can now detect the system's default feed reader and use it. (bug 471346)
- HTML5 Websockets are now available to website authors. (bug 472529)
FF 3.6 and DevPreview relnotes provide some info.
- WOFF format for website fonts (bug 507970).
- Resizeable text areas in web forms (bug 442228).
- Fullscreen video (bug 453063).
- JIT tracing for x86_64 (bug 489146).
- async places history expiration.
- Expiration and frecency-ordered form field autocomplete.
- Improved js-ctypes support.
- Better performance on startup and shutdown.
- SVG attributes which are mapped to CSS properties can now be animated using SMIL (bug 534028). Support for SMIL Animation in SVG.
- Core Animation rendering model for plugins on Mac OS X has been implemented. Plugins which also support this rendering model can now draw faster and more efficiently.
- Support for new CSS attributes such as gradients, background sizing, and pointer events.
- Support for new DOM and HTML5 specifications including the Drag & Drop API and the File API, which allow for more interactive web pages. (bug 500328, bug 457800, bug 356295, bug 523771, bug 503943, bug 396392, and more)
- Protection from out-of-date plugins
- CSS :visited selectors have been changed to block ways that websites can quickly check a user's browsing history.
- The SSL security system has been changed to fix a renegotiation flaw.
- Support for CSS Transitions.
- Support for WebGL, for Direct2D acceleration on Windows (all disabled by default).
- A new HTML5 parser.
- New Troubleshooting Information page (about:support, bug 545110).
- Notification bars for MailNews return receipts (MDN, bug 539066)
- Support for libnotify-based Desktop Notifications on Linux (e.g. mail alerts, finished downloads)
- Support for using system proxy settings on Windows (bug 485764).