diff --git a/bundles/org.eclipse.swt/Eclipse SWT Browser/win32/org/eclipse/swt/browser/Edge.java b/bundles/org.eclipse.swt/Eclipse SWT Browser/win32/org/eclipse/swt/browser/Edge.java
index 9619f0defce..4243495a64a 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT Browser/win32/org/eclipse/swt/browser/Edge.java	
+++ b/bundles/org.eclipse.swt/Eclipse SWT Browser/win32/org/eclipse/swt/browser/Edge.java	
@@ -185,8 +185,8 @@ private static record MouseRelatedDomEvent(String eventType, boolean altKey, boo
 			HttpCookie parser = HttpCookie.parse(CookieValue).get(0);
 			URL origin;
 			try {
-				origin = new URL(CookieUrl);
-			} catch (MalformedURLException e) {
+				origin = new URI(CookieUrl).toURL();
+			} catch (URISyntaxException | IllegalArgumentException | MalformedURLException e) {
 				return;
 			}
 			if (parser.getDomain() == null) {
diff --git a/bundles/org.eclipse.swt/Eclipse SWT Browser/win32/org/eclipse/swt/browser/IE.java b/bundles/org.eclipse.swt/Eclipse SWT Browser/win32/org/eclipse/swt/browser/IE.java
index a733a0600db..0eca21a3287 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT Browser/win32/org/eclipse/swt/browser/IE.java	
+++ b/bundles/org.eclipse.swt/Eclipse SWT Browser/win32/org/eclipse/swt/browser/IE.java	
@@ -717,8 +717,8 @@ else if (IEVersion >= 8) {
 					boolean isPDF = false;
 					String path = null;
 					try {
-						path = new URL(url3).getPath();
-					} catch (MalformedURLException e) {
+						path = new URI(url3).toURL().getPath();
+					} catch (URISyntaxException | IllegalArgumentException | MalformedURLException e) {
 					}
 					if (path != null) {
 						int extensionIndex = path.lastIndexOf('.');
diff --git a/bundles/org.eclipse.swt/Eclipse SWT WebKit/gtk/org/eclipse/swt/browser/WebKit.java b/bundles/org.eclipse.swt/Eclipse SWT WebKit/gtk/org/eclipse/swt/browser/WebKit.java
index 7846cdbfba2..d3ad33a5708 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT WebKit/gtk/org/eclipse/swt/browser/WebKit.java	
+++ b/bundles/org.eclipse.swt/Eclipse SWT WebKit/gtk/org/eclipse/swt/browser/WebKit.java	
@@ -2063,20 +2063,22 @@ public boolean setUrl (String url, String postData, String[] headers) {
 	* invalid URL string and try to fix it by prepending an appropriate protocol.
 	*/
 	try {
-		new URL(url);
-	} catch (MalformedURLException e) {
-		String testUrl = null;
-		if (url.charAt (0) == SEPARATOR_FILE) {
-			/* appears to be a local file */
-			testUrl = PROTOCOL_FILE + url;
-		} else {
-			testUrl = PROTOCOL_HTTP + url;
-		}
-		try {
-			new URL (testUrl);
-			url = testUrl;		/* adding the protocol made the url valid */
-		} catch (MalformedURLException e2) {
-			/* adding the protocol did not make the url valid, so do nothing */
+		new URI(url).toURL();
+	} catch (URISyntaxException | IllegalArgumentException | MalformedURLException e) {
+		if (!url.isEmpty()) {
+			String testUrl = null;
+			if (url.charAt (0) == SEPARATOR_FILE) {
+				/* appears to be a local file */
+				testUrl = PROTOCOL_FILE + url;
+			} else {
+				testUrl = PROTOCOL_HTTP + url;
+			}
+			try {
+				new URI(testUrl).toURL();
+				url = testUrl;		/* adding the protocol made the url valid */
+			} catch (URISyntaxException | IllegalArgumentException | MalformedURLException e2) {
+				/* adding the protocol did not make the url valid, so do nothing */
+			}
 		}
 	}
 
@@ -2137,7 +2139,7 @@ public boolean setUrl (String url, String postData, String[] headers) {
 			String mime_type = null;
 			String encoding_type = null;
 			try {
-				URL base = new URL(base_url);
+				URL base = new URI(base_url).toURL();
 				URLConnection url_conn = base.openConnection();
 				if (url_conn instanceof HttpURLConnection) {
 					HttpURLConnection conn = (HttpURLConnection) url_conn;
@@ -2201,8 +2203,12 @@ public boolean setUrl (String url, String postData, String[] headers) {
 							}
 						}
 					}
+				} else {
+					html = "Unsupported connection type: " + url_conn;
 				}
-			} catch (IOException e) { // MalformedURLException is an IOException also.
+			} catch (URISyntaxException | IllegalArgumentException | MalformedURLException e) {
+				html = "URL is invalid: " + e.getMessage();
+			} catch (IOException e) {
 				html = e.getMessage();
 			} finally {
 				if (html != null && lastRequest == w2_bug527738LastRequestCounter.get()) {
diff --git a/tests/org.eclipse.swt.tests/JUnit Tests/org/eclipse/swt/tests/junit/Test_org_eclipse_swt_browser_Browser.java b/tests/org.eclipse.swt.tests/JUnit Tests/org/eclipse/swt/tests/junit/Test_org_eclipse_swt_browser_Browser.java
index 0b8d191043a..c3bf2aaebcc 100644
--- a/tests/org.eclipse.swt.tests/JUnit Tests/org/eclipse/swt/tests/junit/Test_org_eclipse_swt_browser_Browser.java	
+++ b/tests/org.eclipse.swt.tests/JUnit Tests/org/eclipse/swt/tests/junit/Test_org_eclipse_swt_browser_Browser.java	
@@ -753,7 +753,7 @@ public void test_LocationListener_LocationListener_ordered_changing () {
 	}));
 	shell.open();
 	browser.setText("You should not see this message.");
-	String url = getValidUrl();
+	String url = getValidFileUrl();
 	browser.setUrl(url);
 	assertTrue(waitForPassCondition(() -> locations.size() == 2));
 	assertTrue(locations.get(0).equals("about:blank") && locations.get(1).contains("testWebsiteWithTitle.html"));
@@ -762,8 +762,10 @@ public void test_LocationListener_LocationListener_ordered_changing () {
 @TempDir
 static Path tempFolder;
 
-private String getValidUrl() {
-	return SwtTestUtil.getPath("testWebsiteWithTitle.html", tempFolder).toUri().toString();
+private String getValidFileUrl() {
+	String url = SwtTestUtil.getPath("testWebsiteWithTitle.html", tempFolder).toUri().toString();
+	assertTrue(url.startsWith("file://"));
+	return url;
 }
 
 @Test
@@ -1183,7 +1185,27 @@ public void test_setUrl_local() {
 	assumeFalse(SwtTestUtil.isCocoa, "Test fails on Mac, see https://github.com/eclipse-platform/eclipse.platform.swt/issues/722");
 	String expectedTitle = "Website Title";
 	Runnable browserSetFunc = () -> {
-		String url = getValidUrl();
+		String url = getValidFileUrl();
+		testLogAppend("URL: " + url);
+		boolean opSuccess = browser.setUrl(url);
+		assertTrue(opSuccess);
+	};
+	validateTitleChanged(expectedTitle, browserSetFunc);
+}
+
+/**
+ * Verifies that an invalid URL (missing file://) will be converted to a valid
+ * URL with the file:// added.
+ */
+@Test
+public void test_setUrl_invalid_url_local() {
+	assumeTrue(SwtTestUtil.isLinux, "Handling of invalid URLs is platform dependent");
+	String expectedTitle = "Website Title";
+	Runnable browserSetFunc = () -> {
+		String url = getValidFileUrl();
+		assertTrue(url.startsWith("file://"));
+		url = url.replaceFirst("^file://", "");
+		assertTrue(url.startsWith("/"));
 		testLogAppend("URL: " + url);
 		boolean opSuccess = browser.setUrl(url);
 		assertTrue(opSuccess);
@@ -1209,6 +1231,30 @@ public void test_setUrl_remote() throws IOException {
 	}
 }
 
+/**
+ * Verifies that an invalid URL (missing http://) will be converted to a valid
+ * URL with the http:// added.
+ */
+@Test
+public void test_setUrl_invalid_url_remote() throws IOException {
+	assumeTrue(SwtTestUtil.isLinux, "Handling of invalid URLs is platform dependent");
+
+	try (var server = new EchoHttpServer()) {
+
+		String validUrl = server.getEchoUrl("test_setUrl_remote");
+		assertTrue(validUrl.startsWith("http://"));
+		String url = validUrl.replaceFirst("^http://", "");
+
+		String expectedTitle = "test_setUrl_remote";
+		Runnable browserSetFunc = () -> {
+			testLog.append("Setting Browser url to:" + url);
+			boolean opSuccess = browser.setUrl(url);
+			assertTrue(opSuccess);
+		};
+		validateTitleChanged(expectedTitle, browserSetFunc);
+	}
+}
+
 @Test
 public void test_setUrl_remote_with_post() throws IOException {
 	try (var server = new EchoHttpServer()) {
@@ -1238,6 +1284,106 @@ public void test_setUrl_remote_with_post() throws IOException {
 	}
 }
 
+@Test
+public void test_setUrl_post_invalid_url() {
+	assumeTrue(SwtTestUtil.isLinux, "Handling of invalid URLs is platform dependent");
+	// Purposefully invalid URL (Note that URLs that become valid with
+	// http:// or file:// prefixed will get converted to their valid URLs
+	String url = "";
+	String postData = "test_setUrl_post_invalid_url";
+
+	Runnable browserSetFunc = () -> {
+		testLog.append("Setting Browser url to:" + url);
+		boolean opSuccess = browser.setUrl(url, postData, null);
+		assertTrue(opSuccess);
+	};
+
+	final AtomicReference<Boolean> completed = new AtomicReference<>(false);
+	browser.addProgressListener(completedAdapter(event -> {
+		testLog.append("ProgressListener fired");
+		completed.set(true);
+	}));
+	browserSetFunc.run();
+	shell.open();
+
+	boolean hasFinished = waitForPassCondition(() -> completed.get().booleanValue());
+	assertTrue(hasFinished);
+
+	String lowerCase = browser.getText().toLowerCase();
+	assertTrue(lowerCase.contains("URL is invalid".toLowerCase()), "Browser getText was: " + browser.getText());
+}
+
+@Test
+public void test_setUrl_post_connection_closes_prematurely() throws IOException {
+	assumeTrue(SwtTestUtil.isLinux, """
+			Handling POST in Linux is handled by SWT, so we need extra testing for the SWT code.
+			This test can be adapted to win32/cocoa, but that would be testing the third-party
+			browser component. Therefore (for now) this test only runs on Linux.
+			""");
+	try (var server = new EchoHttpServer() {
+		@Override
+		protected void handlePostEcho(HttpExchange exchange) {
+			// Immediately close the connection - this should generate a user
+			// visible error in the UI.
+
+			// For Webkit case where we handle post
+			exchange.close();
+		}
+	}) {
+		String url = server.postEchoUrl();
+		String postData = "test_setUrl_remote_with_post";
+
+		Runnable browserSetFunc = () -> {
+			testLog.append("Setting Browser url to:" + url);
+			boolean opSuccess = browser.setUrl(url, postData, null);
+			assertTrue(opSuccess);
+		};
+
+		final AtomicReference<Boolean> completed = new AtomicReference<>(false);
+		browser.addProgressListener(completedAdapter(event -> {
+			testLog.append("ProgressListener fired");
+			completed.set(true);
+		}));
+		browserSetFunc.run();
+		shell.open();
+
+		boolean hasFinished = waitForPassCondition(() -> completed.get().booleanValue());
+		assertTrue(hasFinished);
+
+		String lowerCase = browser.getText().toLowerCase();
+		assertTrue(lowerCase.contains("Unexpected end of file from server".toLowerCase()), "Browser getText was: " + browser.getText());
+	}
+}
+
+@Test
+public void test_setUrl_post_file_url() {
+	assumeTrue(SwtTestUtil.isLinux, "Handling of invalid URLs is platform dependent");
+	// Purposefully invalid URL (Note that URLs that become valid with
+	// http:// or file:// prefixed will get converted to their valid URLs
+	String url = getValidFileUrl();
+	String postData = "test_setUrl_post_file_url";
+
+	Runnable browserSetFunc = () -> {
+		testLog.append("Setting Browser url to:" + url);
+		boolean opSuccess = browser.setUrl(url, postData, null);
+		assertTrue(opSuccess);
+	};
+
+	final AtomicReference<Boolean> completed = new AtomicReference<>(false);
+	browser.addProgressListener(completedAdapter(event -> {
+		testLog.append("ProgressListener fired");
+		completed.set(true);
+	}));
+	browserSetFunc.run();
+	shell.open();
+
+	boolean hasFinished = waitForPassCondition(() -> completed.get().booleanValue());
+	assertTrue(hasFinished);
+
+	String lowerCase = browser.getText().toLowerCase();
+	assertTrue(lowerCase.contains("Unsupported connection type".toLowerCase()), "Browser getText was: " + browser.getText());
+}
+
 private void validateTitleChanged(String expectedTitle, Runnable browserSetFunc) {
 	final AtomicReference<String> actualTitle = new AtomicReference<>("");
 	browser.addTitleListener(event ->  {