Supports running in Java 9. Note that this does not yet mean that GWT can compile Java 9 sources, or support the Java 9 JRE changes, but that a Java 9 JRE can be used to compile a GWT project. Do note that the new --module-path flag is not supported, but-classpath must still be used as in the past.
Chrome 61 removed functionality that had been used for reading the absolute top/left values. The internal implementation has been updated to reflect modern standards.
Uncaught exception handler will now receive all errors on the page, as handled bywindow.onerror. This may potentially be a breaking change if there were misbehaving scripts on the page. To disable this functionality, set the propertygwt.uncaughtexceptionhandler.windowonerror to IGNORE:
Super Dev Mode is now the default. DevMode automatically starts Super Dev Mode and reloading a web page automatically runs the compiler when necessary. (The -noSuperDevMode flag may be used to revert to the old behavior.)
Compiling in Super Dev Mode is much faster after the first compile.
gwttar files are incorrect. (Fixed in the next version.)
GWT Designer doesn’t work with 2.7 and is no longer supported. (Source code is available if someone wishes to revive this project.)
IFrameLinker and XSLinker are deprecated because they don’t work in Super Dev Mode. However, we don’t have suitable replacements for all use cases yet. For updates and possible workarounds, see issue 8997.
In draft mode and Super Dev Mode, all compiler optimizations are turned off for better debugging. For example, null pointers are detected sooner.
JSNI references no longer require fully qualified class names when this wouldn’t be necessary in Java. (For example, imports work.)
Significant performance improvements in String, ArrayList, HashMap, and Exception.
New emulated classes: Locale, NavigableSet, and NavigableMap.
New emulated methods in Class, String, Exception, RuntimeException, Logger, Arrays, Collections, and Map.Entry.
LinkedList extends Deque and handles incorrect usage better.
Logging and Stack Traces
GWT apps that inherit the com.google.gwt.logging.Logging module have different default behavior for messages logged using the java.util.logging package. The new default is to log messages at level SEVEREand above to the browser’s console. PopupLogHandler and SystemHandler are no longer enabled by default.
FirebugLogHandler and NullLoggingPopup have been removed. ()
Experimental GSS support
The CssResource.enableGss configuration property turns on GSS support.
When enabled, GSS can be used in a UiBinder file by setting gss=true on a ui:style tag.
If the CssResource.legacy configuration property is set, .css resources and ui:style tags without gss=true will first be converted to GSS and then parsed as GSS.
The ui:data tag has new attributes: mimeType and doNotEmbed.
The rpc.XserializeFinalFields configuration property turns on experimental support for serializing final fields.
LinkedHashSet may be serialized without a serialization policy.
deRPC is removed.
Support overridden methods and generics better.
Fix support for @SkipInterfaceValidation on RequestContext methods.
Upgraded to CLDR 25.
Browser API changes
Updated support for typed arrays.
Fixed an issue with Window.addWindowScrollHandler on Chrome.
The deprecated com.google.gwt.widgets package is removed.
Various bugfixes and minor improvements.
Developer Tool Changes
The -noSuperDevMode flag may be used to turn off Super Dev Mode and revert to old Dev Mode. (However, most current browsers no longer support Dev Mode plugins.)
The -modulePathPrefix flag may be used to move DevMode’s output to a subdirectory of the war directory.
Super Dev Mode
Compiling is much faster after the first compile. (Compiling is skipped altogether if no files have changed.)
The first compile no longer happens at startup.
Chrome reloads the page faster while debugging. (Sourcemap file size is reduced.)
The -launcherDir flag may be used to avoid running the GWT compiler before starting Super Dev Mode. When enabled, Super Dev Mode writes stub .nocache.js files that automatically recompile the GWT app before loading it. Therefore the bookmarklets aren’t needed. (This feature is automatically enabled when launched via DevMode.)
The -logLevel flag may be used to adjust how compile errors are reported.
The Dev Mode On bookmarklet dialog shows whether Super Dev Mode is turned on for each module on the page.
Messages logged using java.util.logging at level SEVERE and above are written to the browser console by default.
Fixed a startup failure caused by locked directories on Windows.
Better error reporting for compile errors while running tests.
Messages logged using java.util.logging at level SEVERE and above are written to the browser console and test output by default.
Removed RunStyleRemoteWeb and the BrowserManager tool.
Removed flags: -standardsMode, -nostandardsMode, -quirksMode. (GWTTestCase tests are always run in an HTML page in standards mode.)