diff --git a/clang-tools-extra/clang-tidy/bugprone/DynamicStaticInitializersCheck.h b/clang-tools-extra/clang-tidy/bugprone/DynamicStaticInitializersCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/DynamicStaticInitializersCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/DynamicStaticInitializersCheck.h
@@ -19,11 +19,12 @@
 /// Finds dynamically initialized static variables in header files.
 ///
 /// The check supports these options:
-///   - `HeaderFileExtensions`: a comma-separated list of filename extensions of
-///     header files (The filename extensions should not contain "." prefix).
-///     "h,hh,hpp,hxx" by default.
+///   - `HeaderFileExtensions`: a semicolon-separated list of filename
+///     extensions of header files (The filename extensions should not contain
+///     "." prefix). ";h;hh;hpp;hxx" by default.
+//
 ///     For extension-less header files, using an empty string or leaving an
-///     empty string between "," if there are other filename extensions.
+///     empty string between ";" if there are other filename extensions.
 class DynamicStaticInitializersCheck : public ClangTidyCheck {
 public:
   DynamicStaticInitializersCheck(StringRef Name, ClangTidyContext *Context);
diff --git a/clang-tools-extra/clang-tidy/bugprone/DynamicStaticInitializersCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/DynamicStaticInitializersCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/DynamicStaticInitializersCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/DynamicStaticInitializersCheck.cpp
@@ -32,7 +32,8 @@
       RawStringHeaderFileExtensions(Options.getLocalOrGlobal(
         "HeaderFileExtensions", utils::defaultHeaderFileExtensions())) {
   if (!utils::parseFileExtensions(RawStringHeaderFileExtensions,
-                                  HeaderFileExtensions, ',')) {
+                                  HeaderFileExtensions,
+                                  utils::defaultFileExtensionDelimiters())) {
     llvm::errs() << "Invalid header file extension: "
                  << RawStringHeaderFileExtensions << "\n";
   }
diff --git a/clang-tools-extra/clang-tidy/google/GlobalNamesInHeadersCheck.h b/clang-tools-extra/clang-tidy/google/GlobalNamesInHeadersCheck.h
--- a/clang-tools-extra/clang-tidy/google/GlobalNamesInHeadersCheck.h
+++ b/clang-tools-extra/clang-tidy/google/GlobalNamesInHeadersCheck.h
@@ -21,11 +21,12 @@
 /// Right now it only triggers on using declarations and directives.
 ///
 /// The check supports these options:
-///   - `HeaderFileExtensions`: a comma-separated list of filename extensions
-///     of header files (the filename extensions should not contain "." prefix).
-///     "h" by default.
+///   - `HeaderFileExtensions`: a semicolon-separated list of filename
+///     extensions of header files (the filename extensions should not contain
+///     "." prefix). ";h;hh;hpp;hxx" by default.
+///
 ///     For extension-less header files, using an empty string or leaving an
-///     empty string between "," if there are other filename extensions.
+///     empty string between ";" if there are other filename extensions.
 class GlobalNamesInHeadersCheck : public ClangTidyCheck {
 public:
   GlobalNamesInHeadersCheck(StringRef Name, ClangTidyContext *Context);
diff --git a/clang-tools-extra/clang-tidy/google/GlobalNamesInHeadersCheck.cpp b/clang-tools-extra/clang-tidy/google/GlobalNamesInHeadersCheck.cpp
--- a/clang-tools-extra/clang-tidy/google/GlobalNamesInHeadersCheck.cpp
+++ b/clang-tools-extra/clang-tidy/google/GlobalNamesInHeadersCheck.cpp
@@ -25,7 +25,8 @@
       RawStringHeaderFileExtensions(Options.getLocalOrGlobal(
           "HeaderFileExtensions", utils::defaultHeaderFileExtensions())) {
   if (!utils::parseFileExtensions(RawStringHeaderFileExtensions,
-                                  HeaderFileExtensions, ',')) {
+                                  HeaderFileExtensions,
+                                  utils::defaultFileExtensionDelimiters())) {
     llvm::errs() << "Invalid header file extension: "
                  << RawStringHeaderFileExtensions << "\n";
   }
diff --git a/clang-tools-extra/clang-tidy/google/UnnamedNamespaceInHeaderCheck.h b/clang-tools-extra/clang-tidy/google/UnnamedNamespaceInHeaderCheck.h
--- a/clang-tools-extra/clang-tidy/google/UnnamedNamespaceInHeaderCheck.h
+++ b/clang-tools-extra/clang-tidy/google/UnnamedNamespaceInHeaderCheck.h
@@ -20,11 +20,12 @@
 /// Finds anonymous namespaces in headers.
 ///
 /// The check supports these options:
-///   - `HeaderFileExtensions`: a comma-separated list of filename extensions of
-///     header files (The filename extensions should not contain "." prefix).
-///     "h,hh,hpp,hxx" by default.
+///   - `HeaderFileExtensions`: a semicolon-separated list of filename
+///     extensions of header files (The filename extensions should not contain
+///     "." prefix). ";h;hh;hpp;hxx" by default.
+///
 ///     For extension-less header files, using an empty string or leaving an
-///     empty string between "," if there are other filename extensions.
+///     empty string between ";" if there are other filename extensions.
 ///
 /// https://google.github.io/styleguide/cppguide.html#Namespaces
 ///
diff --git a/clang-tools-extra/clang-tidy/google/UnnamedNamespaceInHeaderCheck.cpp b/clang-tools-extra/clang-tidy/google/UnnamedNamespaceInHeaderCheck.cpp
--- a/clang-tools-extra/clang-tidy/google/UnnamedNamespaceInHeaderCheck.cpp
+++ b/clang-tools-extra/clang-tidy/google/UnnamedNamespaceInHeaderCheck.cpp
@@ -24,7 +24,8 @@
       RawStringHeaderFileExtensions(Options.getLocalOrGlobal(
           "HeaderFileExtensions", utils::defaultHeaderFileExtensions())) {
   if (!utils::parseFileExtensions(RawStringHeaderFileExtensions,
-                                  HeaderFileExtensions, ',')) {
+                                  HeaderFileExtensions,
+                                  utils::defaultFileExtensionDelimiters())) {
     llvm::errs() << "Invalid header file extension: "
                  << RawStringHeaderFileExtensions << "\n";
   }
diff --git a/clang-tools-extra/clang-tidy/llvm/HeaderGuardCheck.h b/clang-tools-extra/clang-tidy/llvm/HeaderGuardCheck.h
--- a/clang-tools-extra/clang-tidy/llvm/HeaderGuardCheck.h
+++ b/clang-tools-extra/clang-tidy/llvm/HeaderGuardCheck.h
@@ -19,11 +19,12 @@
 /// For the user-facing documentation see:
 /// http://clang.llvm.org/extra/clang-tidy/checks/llvm-header-guard.html
 /// The check supports these options:
-///   - `HeaderFileExtensions`: a comma-separated list of filename extensions of
-///     header files (The filename extension should not contain "." prefix).
-///     ",h,hh,hpp,hxx" by default.
+///   - `HeaderFileExtensions`: a semicolon-separated list of filename
+///     extensions of header files (The filename extension should not contain
+///     "." prefix). ";h;hh;hpp;hxx" by default.
+///
 ///     For extension-less header files, using an empty string or leaving an
-///     empty string between "," if there are other filename extensions.
+///     empty string between ";" if there are other filename extensions.
 class LLVMHeaderGuardCheck : public utils::HeaderGuardCheck {
 public:
   LLVMHeaderGuardCheck(StringRef Name, ClangTidyContext *Context);
diff --git a/clang-tools-extra/clang-tidy/misc/DefinitionsInHeadersCheck.h b/clang-tools-extra/clang-tidy/misc/DefinitionsInHeadersCheck.h
--- a/clang-tools-extra/clang-tidy/misc/DefinitionsInHeadersCheck.h
+++ b/clang-tools-extra/clang-tidy/misc/DefinitionsInHeadersCheck.h
@@ -22,11 +22,12 @@
 /// The check supports these options:
 ///   - `UseHeaderFileExtension`: Whether to use file extension to distinguish
 ///     header files. True by default.
-///   - `HeaderFileExtensions`: a comma-separated list of filename extensions of
-///     header files (The filename extension should not contain "." prefix).
-///     ",h,hh,hpp,hxx" by default.
+///   - `HeaderFileExtensions`: a semicolon-separated list of filename
+///     extensions of header files (The filename extension should not contain
+///     "." prefix). ";h;hh;hpp;hxx" by default.
+///
 ///     For extension-less header files, using an empty string or leaving an
-///     empty string between "," if there are other filename extensions.
+///     empty string between ";" if there are other filename extensions.
 ///
 /// For the user-facing documentation see:
 /// http://clang.llvm.org/extra/clang-tidy/checks/misc-definitions-in-headers.html
diff --git a/clang-tools-extra/clang-tidy/misc/DefinitionsInHeadersCheck.cpp b/clang-tools-extra/clang-tidy/misc/DefinitionsInHeadersCheck.cpp
--- a/clang-tools-extra/clang-tidy/misc/DefinitionsInHeadersCheck.cpp
+++ b/clang-tools-extra/clang-tidy/misc/DefinitionsInHeadersCheck.cpp
@@ -34,7 +34,8 @@
       RawStringHeaderFileExtensions(Options.getLocalOrGlobal(
           "HeaderFileExtensions", utils::defaultHeaderFileExtensions())) {
   if (!utils::parseFileExtensions(RawStringHeaderFileExtensions,
-                                  HeaderFileExtensions, ',')) {
+                                  HeaderFileExtensions,
+                                  utils::defaultFileExtensionDelimiters())) {
     // FIXME: Find a more suitable way to handle invalid configuration
     // options.
     llvm::errs() << "Invalid header file extension: "
diff --git a/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.h b/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.h
--- a/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.h
+++ b/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.h
@@ -34,11 +34,16 @@
 
 /// Returns recommended default value for the list of header file
 /// extensions.
-inline StringRef defaultHeaderFileExtensions() { return ",h,hh,hpp,hxx"; }
+inline StringRef defaultHeaderFileExtensions() { return ";h;hh;hpp;hxx"; }
+
+/// Returns recommended default value for the list of file extension
+/// delimiters.
+inline StringRef defaultFileExtensionDelimiters() { return ",;"; }
 
 /// Parses header file extensions from a semicolon-separated list.
 bool parseFileExtensions(StringRef AllFileExtensions,
-                         FileExtensionsSet &FileExtensions, char Delimiter);
+                         FileExtensionsSet &FileExtensions,
+                         StringRef Delimiters);
 
 /// Decides whether a file has one of the specified file extensions.
 bool isFileExtension(StringRef FileName,
diff --git a/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.cpp b/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.cpp
--- a/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.cpp
+++ b/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.cpp
@@ -33,9 +33,16 @@
 }
 
 bool parseFileExtensions(StringRef AllFileExtensions,
-                         FileExtensionsSet &FileExtensions, char Delimiter) {
+                         FileExtensionsSet &FileExtensions,
+                         StringRef Delimiters) {
   SmallVector<StringRef, 5> Suffixes;
-  AllFileExtensions.split(Suffixes, Delimiter);
+  for (char Delimiter : Delimiters) {
+    if (AllFileExtensions.contains(Delimiter)) {
+      AllFileExtensions.split(Suffixes, Delimiter);
+      break;
+    }
+  }
+
   FileExtensions.clear();
   for (StringRef Suffix : Suffixes) {
     StringRef Extension = Suffix.trim();
diff --git a/clang-tools-extra/clang-tidy/utils/HeaderGuard.h b/clang-tools-extra/clang-tidy/utils/HeaderGuard.h
--- a/clang-tools-extra/clang-tidy/utils/HeaderGuard.h
+++ b/clang-tools-extra/clang-tidy/utils/HeaderGuard.h
@@ -18,11 +18,12 @@
 
 /// Finds and fixes header guards.
 /// The check supports these options:
-///   - `HeaderFileExtensions`: a comma-separated list of filename extensions of
-///     header files (The filename extension should not contain "." prefix).
-///     ",h,hh,hpp,hxx" by default.
+///   - `HeaderFileExtensions`: a semicolon-separated list of filename
+///     extensions of header files (The filename extension should not contain
+///     "." prefix). ";h;hh;hpp;hxx" by default.
+///
 ///     For extension-less header files, using an empty string or leaving an
-///     empty string between "," if there are other filename extensions.
+///     empty string between ";" if there are other filename extensions.
 class HeaderGuardCheck : public ClangTidyCheck {
 public:
   HeaderGuardCheck(StringRef Name, ClangTidyContext *Context)
@@ -30,7 +31,8 @@
         RawStringHeaderFileExtensions(Options.getLocalOrGlobal(
             "HeaderFileExtensions", utils::defaultHeaderFileExtensions())) {
     utils::parseFileExtensions(RawStringHeaderFileExtensions,
-                               HeaderFileExtensions, ',');
+                               HeaderFileExtensions,
+                               utils::defaultFileExtensionDelimiters());
   }
   void registerPPCallbacks(const SourceManager &SM, Preprocessor *PP,
                            Preprocessor *ModuleExpanderPP) override;
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -125,6 +125,11 @@
   check now detects in class initializers and constructor initializers which
   are deemed to be redundant.
 
+- Checks supporting the ``HeaderFileExtensions`` flag now support ``;`` as a
+  delimiter in addition to ``,``, with the latter being deprecated as of this
+  release. This simplifies how one specifies the options on the command line:
+  ``--config="{CheckOptions: [{ key: HeaderFileExtensions, value: h;;hpp;hxx }]}"``
+
 Renamed checks
 ^^^^^^^^^^^^^^