diff --git a/CONTRIBUTING.rst b/CONTRIBUTING.rst
index ebd3ed355a..d62afa5751 100644
--- a/CONTRIBUTING.rst
+++ b/CONTRIBUTING.rst
@@ -34,7 +34,7 @@ code.  It automatically runs ``clang-format`` on the set of source files
 for which we enforce style.  The script also has options to format only
 a subset of files, such as those that are locally modified.
 
-.. _`clang-format`: http://clang.llvm.org/docs/ClangFormat.html
+.. _`clang-format`: https://clang.llvm.org/docs/ClangFormat.html
 .. _`.clang-format`: .clang-format
 .. _`clang-format.bash`: clang-format.bash
 
diff --git a/Directory.cxx b/Directory.cxx
index f239576efe..f152ca4e01 100644
--- a/Directory.cxx
+++ b/Directory.cxx
@@ -269,7 +269,7 @@ unsigned long Directory::GetNumberOfFilesInDirectory(const std::string& name,
 #  include <string.h>
 
 // PGI with glibc has trouble with dirent and large file support:
-//  http://www.pgroup.com/userforum/viewtopic.php?
+//  https://www.pgroup.com/userforum/viewtopic.php?
 //  p=1992&sid=f16167f51964f1a68fe5041b8eb213b6
 // Work around the problem by mapping dirent the same way as readdir.
 #  if defined(__PGI) && defined(__GLIBC__)
diff --git a/MD5.c b/MD5.c
index 76995e22f0..b0faa0ebca 100644
--- a/MD5.c
+++ b/MD5.c
@@ -52,7 +52,7 @@
 
   This code implements the MD5 Algorithm defined in RFC 1321, whose
   text is available at
-        http://www.ietf.org/rfc/rfc1321.txt
+        https://www.ietf.org/rfc/rfc1321.txt
   The code is derived from the text of the RFC, including the test suite
   (section A.5) but excluding the rest of Appendix A.  It does not include
   any code or documentation that is identified in the RFC as being
diff --git a/SystemInformation.cxx b/SystemInformation.cxx
index 37526dcc72..5e07e80aaf 100644
--- a/SystemInformation.cxx
+++ b/SystemInformation.cxx
@@ -22,10 +22,10 @@
 // Consider using these on Win32/Win64 for some of them:
 //
 // IsProcessorFeaturePresent
-// http://msdn.microsoft.com/en-us/library/ms724482(VS.85).aspx
+// https://msdn.microsoft.com/en-us/library/ms724482(VS.85).aspx
 //
 // GetProcessMemoryInfo
-// http://msdn.microsoft.com/en-us/library/ms683219(VS.85).aspx
+// https://msdn.microsoft.com/en-us/library/ms683219(VS.85).aspx
 
 #include "kwsysPrivate.h"
 #include KWSYS_HEADER(SystemInformation.hxx)
@@ -4265,7 +4265,7 @@ bool SystemInformationImplementation::QueryCygwinMemory()
 {
 #ifdef __CYGWIN__
   // _SC_PAGE_SIZE does return the mmap() granularity on Cygwin,
-  // see http://cygwin.com/ml/cygwin/2006-06/msg00350.html
+  // see https://sourceware.org/legacy-ml/cygwin/2006-06/msg00350.html
   // Therefore just use 4096 as the page size of Windows.
   long m = sysconf(_SC_PHYS_PAGES);
   if (m < 0) {
diff --git a/SystemTools.cxx b/SystemTools.cxx
index 3f714decbe..11018a6bef 100644
--- a/SystemTools.cxx
+++ b/SystemTools.cxx
@@ -4875,7 +4875,7 @@ SystemToolsManager::~SystemToolsManager()
 
 #if defined(__VMS)
 // On VMS we configure the run time C library to be more UNIX like.
-// http://h71000.www7.hp.com/doc/732final/5763/5763pro_004.html
+// https://h71000.www7.hp.com/doc/732final/5763/5763pro_004.html
 extern "C" int decc$feature_get_index(char* name);
 extern "C" int decc$feature_set_value(int index, int mode, int value);
 static int SetVMSFeature(char* name, int value)
diff --git a/Terminal.c b/Terminal.c
index 39081a7527..eb6e01b5ec 100644
--- a/Terminal.c
+++ b/Terminal.c
@@ -168,7 +168,7 @@ static const char* kwsysTerminalVT100Names[] = { "Eterm",
 static int kwsysTerminalStreamIsVT100(FILE* stream, int default_vt100,
                                       int default_tty)
 {
-  /* Force color according to http://bixense.com/clicolors/ convention.  */
+  /* Force color according to https://bixense.com/clicolors/ convention.  */
   {
     const char* clicolor_force = getenv("CLICOLOR_FORCE");
     if (clicolor_force && *clicolor_force &&
@@ -177,7 +177,7 @@ static int kwsysTerminalStreamIsVT100(FILE* stream, int default_vt100,
     }
   }
 
-  /* Disable color according to http://bixense.com/clicolors/ convention. */
+  /* Disable color according to https://bixense.com/clicolors/ convention. */
   {
     const char* clicolor = getenv("CLICOLOR");
     if (clicolor && strcmp(clicolor, "0") == 0) {
diff --git a/testSystemTools.cxx b/testSystemTools.cxx
index 8afcb68273..9275043141 100644
--- a/testSystemTools.cxx
+++ b/testSystemTools.cxx
@@ -1148,12 +1148,12 @@ static bool CheckCopyFileIfDifferent()
 static bool CheckURLParsing()
 {
   bool ret = true;
-  std::string url = "http://user:pw@hostname:42/full/url.com";
+  std::string url = "https://user:pw@hostname:42/full/url.com";
 
   std::string protocol, username, password, hostname, dataport, database;
   kwsys::SystemTools::ParseURL(url, protocol, username, password, hostname,
                                dataport, database);
-  if (protocol != "http" || username != "user" || password != "pw" ||
+  if (protocol != "https" || username != "user" || password != "pw" ||
       hostname != "hostname" || dataport != "42" ||
       database != "full/url.com") {
     std::cerr << "Incorrect URL parsing" << std::endl;