diff --git a/Texassemble/texassemble.cpp b/Texassemble/texassemble.cpp
index 68edbc4..34aff99 100644
--- a/Texassemble/texassemble.cpp
+++ b/Texassemble/texassemble.cpp
@@ -78,6 +78,7 @@ enum OPTIONS
     OPT_SRGBO,
     OPT_SRGB,
     OPT_OUTPUTFILE,
+    OPT_TOLOWER,
     OPT_OVERWRITE,
     OPT_USE_DX10,
     OPT_NOLOGO,
@@ -136,6 +137,7 @@ const SValue g_pOptions[] =
     { L"srgbo",     OPT_SRGBO },
     { L"srgb",      OPT_SRGB },
     { L"o",         OPT_OUTPUTFILE },
+    { L"l",         OPT_TOLOWER },
     { L"y",         OPT_OVERWRITE },
     { L"dx10",      OPT_USE_DX10 },
     { L"nologo",    OPT_NOLOGO },
@@ -519,6 +521,7 @@ namespace
         wprintf(L"   -if <filter>        image filtering\n");
         wprintf(L"   -srgb{i|o}          sRGB {input, output}\n");
         wprintf(L"   -o <filename>       output filename\n");
+        wprintf(L"   -l                  force output filename to lower case\n");
         wprintf(L"   -y                  overwrite existing output file (if any)\n");
         wprintf(L"   -sepalpha           resize alpha channel separately from color channels\n");
         wprintf(L"   -nowic              Force non-WIC filtering\n");
@@ -1885,6 +1888,11 @@ int __cdecl wmain(_In_ int argc, _In_z_count_(argc) wchar_t* argv[])
         wprintf(L"\n");
         fflush(stdout);
 
+        if (dwOptions & (1 << OPT_TOLOWER))
+        {
+            (void)_wcslwr_s(szOutputFile);
+        }
+
         if (~dwOptions & (1 << OPT_OVERWRITE))
         {
             if (GetFileAttributesW(szOutputFile) != INVALID_FILE_ATTRIBUTES)
@@ -1967,6 +1975,11 @@ int __cdecl wmain(_In_ int argc, _In_z_count_(argc) wchar_t* argv[])
         wprintf(L"\n");
         fflush(stdout);
 
+        if (dwOptions & (1 << OPT_TOLOWER))
+        {
+            (void)_wcslwr_s(szOutputFile);
+        }
+
         if (~dwOptions & (1 << OPT_OVERWRITE))
         {
             if (GetFileAttributesW(szOutputFile) != INVALID_FILE_ATTRIBUTES)
@@ -2033,6 +2046,11 @@ int __cdecl wmain(_In_ int argc, _In_z_count_(argc) wchar_t* argv[])
         wprintf(L"\n");
         fflush(stdout);
 
+        if (dwOptions & (1 << OPT_TOLOWER))
+        {
+            (void)_wcslwr_s(szOutputFile);
+        }
+
         if (~dwOptions & (1 << OPT_OVERWRITE))
         {
             if (GetFileAttributesW(szOutputFile) != INVALID_FILE_ATTRIBUTES)
@@ -2100,6 +2118,11 @@ int __cdecl wmain(_In_ int argc, _In_z_count_(argc) wchar_t* argv[])
         wprintf(L"\n");
         fflush(stdout);
 
+        if (dwOptions & (1 << OPT_TOLOWER))
+        {
+            (void)_wcslwr_s(szOutputFile);
+        }
+
         if (~dwOptions & (1 << OPT_OVERWRITE))
         {
             if (GetFileAttributesW(szOutputFile) != INVALID_FILE_ATTRIBUTES)
diff --git a/Texconv/texconv.cpp b/Texconv/texconv.cpp
index 6fdcc9b..aecdc11 100644
--- a/Texconv/texconv.cpp
+++ b/Texconv/texconv.cpp
@@ -68,6 +68,7 @@ enum OPTIONS
     OPT_PREFIX,
     OPT_SUFFIX,
     OPT_OUTPUTDIR,
+    OPT_TOLOWER,
     OPT_OVERWRITE,
     OPT_FILETYPE,
     OPT_HFLIP,
@@ -157,6 +158,7 @@ const SValue g_pOptions[] =
     { L"px",            OPT_PREFIX },
     { L"sx",            OPT_SUFFIX },
     { L"o",             OPT_OUTPUTDIR },
+    { L"l",             OPT_TOLOWER },
     { L"y",             OPT_OVERWRITE },
     { L"ft",            OPT_FILETYPE },
     { L"hflip",         OPT_HFLIP },
@@ -720,6 +722,7 @@ namespace
         wprintf(L"\n   -px <string>        name prefix\n");
         wprintf(L"   -sx <string>        name suffix\n");
         wprintf(L"   -o <directory>      output directory\n");
+        wprintf(L"   -l                  force output filename to lower case\n");
         wprintf(L"   -y                  overwrite existing output file (if any)\n");
         wprintf(L"   -ft <filetype>      output file type\n");
         wprintf(L"\n   -hflip              horizonal flip of source image\n");
@@ -3066,6 +3069,11 @@ int __cdecl wmain(_In_ int argc, _In_z_count_(argc) wchar_t* argv[])
 
             wcscat_s(pConv->szDest, MAX_PATH, szSuffix);
 
+            if (dwOptions & (DWORD64(1) << OPT_TOLOWER))
+            {
+                (void)_wcslwr_s(pConv->szDest);
+            }
+
             // Write texture
             wprintf(L"writing %ls", pConv->szDest);
             fflush(stdout);
diff --git a/Texdiag/texdiag.cpp b/Texdiag/texdiag.cpp
index 459d273..c2cee71 100644
--- a/Texdiag/texdiag.cpp
+++ b/Texdiag/texdiag.cpp
@@ -64,6 +64,7 @@ enum OPTIONS
     OPT_DDS_DWORD_ALIGN,
     OPT_DDS_BAD_DXTN_TAILS,
     OPT_OUTPUTFILE,
+    OPT_TOLOWER,
     OPT_OVERWRITE,
     OPT_FILETYPE,
     OPT_NOLOGO,
@@ -113,6 +114,7 @@ const SValue g_pOptions[] =
     { L"badtails",  OPT_DDS_BAD_DXTN_TAILS },
     { L"nologo",    OPT_NOLOGO },
     { L"o",         OPT_OUTPUTFILE },
+    { L"l",         OPT_TOLOWER },
     { L"y",         OPT_OVERWRITE },
     { L"ft",        OPT_FILETYPE },
     { L"tu",        OPT_TYPELESS_UNORM },
@@ -549,6 +551,7 @@ namespace
         wprintf(L"\n                       (diff only)\n");
         wprintf(L"   -f <format>         format\n");
         wprintf(L"   -o <filename>       output filename\n");
+        wprintf(L"   -l                  force output filename to lower case\n");
         wprintf(L"   -y                  overwrite existing output file (if any)\n");
         wprintf(L"\n                       (dumpbc only)\n");
         wprintf(L"   -targetx <num>      dump pixels at location x (defaults to all)\n");
@@ -3368,6 +3371,11 @@ int __cdecl wmain(_In_ int argc, _In_z_count_(argc) wchar_t* argv[])
                     return 1;
                 }
 
+                if (dwOptions & (1 << OPT_TOLOWER))
+                {
+                    (void)_wcslwr_s(szOutputFile);
+                }
+
                 if (~dwOptions & (1 << OPT_OVERWRITE))
                 {
                     if (GetFileAttributesW(szOutputFile) != INVALID_FILE_ATTRIBUTES)