diff --git a/src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/formats/html/ExternalSpecsWriter.java b/src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/formats/html/ExternalSpecsWriter.java
index 4583f78c59d..f71df85f64a 100644
--- a/src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/formats/html/ExternalSpecsWriter.java
+++ b/src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/formats/html/ExternalSpecsWriter.java
@@ -132,7 +132,7 @@ public class ExternalSpecsWriter extends HtmlDocletWriter {
         for (IndexItem ii : configuration.mainIndex.getItems(DocTree.Kind.SPEC)) {
             if (ii.getDocTree() instanceof SpecTree st) {
                 String url = st.getURL().toString();
-                String title = st.getTitle().toString();
+                String title = ii.getLabel(); // normalized form of  st.getTitle()
                 itemsByTitle
                         .computeIfAbsent(title, l -> new HashMap<>())
                         .computeIfAbsent(url, u -> new ArrayList<>())
diff --git a/src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/formats/html/TagletWriterImpl.java b/src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/formats/html/TagletWriterImpl.java
index dc3f51eb9a6..5481814907a 100644
--- a/src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/formats/html/TagletWriterImpl.java
+++ b/src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/formats/html/TagletWriterImpl.java
@@ -222,9 +222,9 @@ public class TagletWriterImpl extends TagletWriter {
         DocTree searchTerm = tag.getSearchTerm();
         String tagText = (searchTerm instanceof TextTree tt) ? tt.getBody() : "";
         if (tagText.charAt(0) == '"' && tagText.charAt(tagText.length() - 1) == '"') {
-            tagText = tagText.substring(1, tagText.length() - 1)
-                             .replaceAll("\\s+", " ");
+            tagText = tagText.substring(1, tagText.length() - 1);
         }
+        tagText = tagText.replaceAll("\\s+", " ");
 
         Content desc = htmlWriter.commentTagsToContent(element, tag.getDescription(), context.within(tag));
         String descText = extractText(desc);
@@ -771,7 +771,8 @@ public class TagletWriterImpl extends TagletWriter {
         String specTreeURL = specTree.getURL().getBody();
         List<? extends DocTree> specTreeLabel = specTree.getTitle();
         Content label = htmlWriter.commentTagsToContent(holder, specTreeLabel, isFirstSentence);
-        return getExternalSpecContent(holder, specTree, specTreeURL, textOf(specTreeLabel), label);
+        return getExternalSpecContent(holder, specTree, specTreeURL,
+                textOf(specTreeLabel).replaceAll("\\s+", " "), label);
     }
 
     Content getExternalSpecContent(Element holder, DocTree docTree, String url, String searchText, Content title) {
diff --git a/test/langtools/jdk/javadoc/doclet/testSpecTag/TestSpecTag.java b/test/langtools/jdk/javadoc/doclet/testSpecTag/TestSpecTag.java
index 02dbc3f3d75..d80fa6feca2 100644
--- a/test/langtools/jdk/javadoc/doclet/testSpecTag/TestSpecTag.java
+++ b/test/langtools/jdk/javadoc/doclet/testSpecTag/TestSpecTag.java
@@ -23,7 +23,7 @@
 
 /*
  * @test
- * @bug 6251738 8226279 8297802 8296546
+ * @bug 6251738 8226279 8297802 8296546 8305407
  * @summary JDK-8226279 javadoc should support a new at-spec tag
  * @library /tools/lib ../../lib
  * @modules jdk.javadoc/jdk.javadoc.internal.tool
@@ -415,6 +415,51 @@ public class TestSpecTag extends JavadocTester {
                     .replace("#FILE#", src.resolve("p").resolve("C.java").toString()));
     }
 
+    @Test
+    public void testDifferentWhitespaceTitlesForURL(Path base) throws IOException {
+        Path src = base.resolve("src");
+        tb.writeJavaFiles(src, """
+                package p;
+                /** Class C. */
+                public class C {
+                    private C() { }
+
+                    /**
+                     * Method m1.
+                     * @spec http://example.com/index.html abc def
+                     */
+                     public void m1() { }
+
+                    /**
+                     * Method m2.
+                     * @spec http://example.com/index.html abc         def
+                     */
+                     public void m2() { }
+                }
+                """);
+
+        javadoc("-d", base.resolve("out").toString(),
+                "--source-path", src.toString(),
+                "p");
+        checkExit(Exit.OK);
+
+        checkOutput(Output.OUT, false, "error");
+
+        checkOutput("external-specs.html", true,
+                """
+                    <div class="summary-table two-column-summary">
+                    <div class="table-header col-first">Specification</div>
+                    <div class="table-header col-last">Referenced In</div>
+                    <div class="col-first even-row-color"><a href="http://example.com/index.html">abc def</a></div>
+                    <div class="col-last even-row-color">
+                    <ul class="ref-list">
+                    <li><code><a href="p/C.html#abcdef">p.C.m1()</a></code></li>
+                    <li><code><a href="p/C.html#abcdef-1">p.C.m2()</a></code></li>
+                    </ul>
+                    </div>
+                    </div>""");
+    }
+
     @Test
     public void testMultipleURLsForTitle(Path base) throws IOException {
         Path src = base.resolve("src");