diff --git a/autotest/CountTrailingZeroBits/CountTrailingZeroBits.cpp b/autotest/CountTrailingZeroBits/CountTrailingZeroBits.cpp
new file mode 100644
index 000000000..a7ba24a05
--- /dev/null
+++ b/autotest/CountTrailingZeroBits/CountTrailingZeroBits.cpp
@@ -0,0 +1,24 @@
+#include <Core/Core.h>
+
+using namespace Upp;
+
+CONSOLE_APP_MAIN
+{
+	StdLogSetup(LOG_FILE|LOG_COUT);
+
+	for(int i = 0; i < 32; i++)
+		DLOG(i << " " << CountTrailingZeroBits(1 << i));
+	DDUMP(CountTrailingZeroBits(0x78));
+	DDUMP(CountTrailingZeroBits(0xf000));
+	DDUMP(CountTrailingZeroBits(0xf0000000));
+
+	for(int i = 0; i < 64; i++)
+		DLOG(i << " " << CountTrailingZeroBits64((uint64)1 << i));
+	DDUMP(CountTrailingZeroBits64(0x78));
+	DDUMP(CountTrailingZeroBits64(0xf000));
+	DDUMP(CountTrailingZeroBits64(0xf0000000));
+	DDUMP(CountTrailingZeroBits64(0xf0000000f0000000));
+	DDUMP(CountTrailingZeroBits64(0xf000000000000000));
+	
+	CheckLogEtalon();
+}
diff --git a/autotest/CountTrailingZeroBits/CountTrailingZeroBits.upp b/autotest/CountTrailingZeroBits/CountTrailingZeroBits.upp
new file mode 100644
index 000000000..d2389914c
--- /dev/null
+++ b/autotest/CountTrailingZeroBits/CountTrailingZeroBits.upp
@@ -0,0 +1,10 @@
+uses
+	Core;
+
+file
+	Etalon.log,
+	CountTrailingZeroBits.cpp;
+
+mainconfig
+	"" = "";
+
diff --git a/autotest/CountTrailingZeroBits/Etalon.log b/autotest/CountTrailingZeroBits/Etalon.log
new file mode 100644
index 000000000..73d6426c2
--- /dev/null
+++ b/autotest/CountTrailingZeroBits/Etalon.log
@@ -0,0 +1,106 @@
+* C:\upp\out\autotest\CLANGx64.Debug.Debug_Full\CountTrailingZeroBits.exe 31.03.2025 11:30:38, user: mirek
+
+0 0
+1 1
+2 2
+3 3
+4 4
+5 5
+6 6
+7 7
+8 8
+9 9
+10 10
+11 11
+12 12
+13 13
+14 14
+15 15
+16 16
+17 17
+18 18
+19 19
+20 20
+21 21
+22 22
+23 23
+24 24
+25 25
+26 26
+27 27
+28 28
+29 29
+30 30
+31 31
+CountTrailingZeroBits(0x78) = 3
+CountTrailingZeroBits(0xf000) = 12
+CountTrailingZeroBits(0xf0000000) = 28
+0 0
+1 1
+2 2
+3 3
+4 4
+5 5
+6 6
+7 7
+8 8
+9 9
+10 10
+11 11
+12 12
+13 13
+14 14
+15 15
+16 16
+17 17
+18 18
+19 19
+20 20
+21 21
+22 22
+23 23
+24 24
+25 25
+26 26
+27 27
+28 28
+29 29
+30 30
+31 31
+32 32
+33 33
+34 34
+35 35
+36 36
+37 37
+38 38
+39 39
+40 40
+41 41
+42 42
+43 43
+44 44
+45 45
+46 46
+47 47
+48 48
+49 49
+50 50
+51 51
+52 52
+53 53
+54 54
+55 55
+56 56
+57 57
+58 58
+59 59
+60 60
+61 61
+62 62
+63 63
+CountTrailingZeroBits64(0x78) = 3
+CountTrailingZeroBits64(0xf000) = 12
+CountTrailingZeroBits64(0xf0000000) = 28
+CountTrailingZeroBits64(0xf0000000f0000000) = 28
+CountTrailingZeroBits64(0xf000000000000000) = 60
diff --git a/uppsrc/Core/Ops.h b/uppsrc/Core/Ops.h
index 8907b44a0..924bed32a 100644
--- a/uppsrc/Core/Ops.h
+++ b/uppsrc/Core/Ops.h
@@ -243,6 +243,55 @@ int CountBits64(uint64 mask)
 #endif
 }
 
+force_inline
+int CountTrailingZeroBits(dword x)
+{
+#if COMPILER_GCC && !defined(flagLEGACY_CPU)
+	return __builtin_ctz(x);
+#elif COMPILER_MSC && !defined(flagLEGACY_CPU)
+	unsigned long index;
+	_BitScanForward(&index, x);
+	return index;
+#else
+	// unlikely fallback
+	int ret = 0;
+	if((x & 0xffff) == 0) {
+		x >>= 16;
+		ret += 16;
+	}
+	if((x & 0xff) == 0) {
+		x >>= 8;
+		ret += 8;
+	}
+	if((x & 0xf) == 0) {
+		x >>= 4;
+		ret += 4;
+	}
+	if((x & 0x3) == 0) {
+		x >>= 2;
+		ret += 2;
+	}
+	if((x & 0x1) == 0)
+		ret += 1;
+	return ret;
+#endif
+}
+
+force_inline
+int CountTrailingZeroBits64(uint64 x)
+{
+#if COMPILER_GCC && !defined(flagLEGACY_CPU)
+	return __builtin_ctzll(x);
+#elif COMPILER_MSC && !defined(flagLEGACY_CPU)
+	unsigned long index;
+	_BitScanForward64(&index, x);
+	return index;
+#else
+	// unlikely fallback
+	return (x & 0xffffffff) ? CountTrailingZeroBits((dword)x) : CountTrailingZeroBits((dword)(x >> 32)) + 32;
+#endif
+}
+
 #if defined(__SIZEOF_INT128__) && (__GNUC__ > 5 || __clang_major__ >= 5)
 
 #ifdef CPU_X86
diff --git a/uppsrc/Core/src.tpp/Mem_en-us.tpp b/uppsrc/Core/src.tpp/Mem_en-us.tpp
index a5a6b3b33..9d8065e43 100644
--- a/uppsrc/Core/src.tpp/Mem_en-us.tpp
+++ b/uppsrc/Core/src.tpp/Mem_en-us.tpp
@@ -114,7 +114,7 @@ onst]_[@(0.0.255) void]_`*[*@3 ptr], [_^size`_t^ size`_t]_[*@3 size])&]
 word]_[*@3 h])&]
 [s2;%% This functions `"hashes all bits together`". One purpose is 
 to bring the entropy of higher bits down so that the hash can 
-be limited by masking, other purpose is to provide hash for integral 
+be limited by masking, other purpose is to provide hash for integer 
 numbers.&]
 [s2;%% &]
 [s4; &]
@@ -139,6 +139,14 @@ loosing the precision.&]
 [s2;%% Returns the total number of set bits in a given bit [%-*@3 mask].&]
 [s3; &]
 [s4; &]
+[s5;:Upp`:`:CountTrailingZeroBits`(dword`): [@(0.0.255) int] [* CountTrailingZeroBits](dw
+ord [*@3 x])&]
+[s5;:Upp`:`:CountTrailingZeroBits64`(uint64`): [@(0.0.255) int] [* CountTrailingZeroBits6
+4](uint64 [*@3 x])&]
+[s2; [%% Returns the index of first non`-zero bit in (from least significant 
+bit). If] [*@3 x] is zero, the result is undefined.&]
+[s3; &]
+[s4; &]
 [s5;:Upp`:`:Peek16le`(const void`*`): [@(0.0.255) int]_[* Peek16le]([@(0.0.255) const]_[@(0.0.255) v
 oid]_`*[*@3 ptr])&]
 [s5;:Upp`:`:Peek32le`(const void`*`): [@(0.0.255) int]_[* Peek32le]([@(0.0.255) const]_[@(0.0.255) v