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How to check if Windows executable is 64-bit reading only its binary. Without executing it and not using any tools like the SDK tool dumpbin.exe with the /headers option.

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2 Answers 2

up vote 19 down vote accepted

Executable type is indicated by PE header, download documentation.

The first word (two bytes) of PE header indicates target machine, here is a list of possible values:

0x0000 - The contents of this field are assumed to be applicable to any machine type
0x01d3 - Matsushita AM33
0x8664 - x64
0x01c0 - ARM little endian
0x01c4 - ARMv7 (or higher) Thumb mode only
0xaa64 - ARMv8 in 64-bit mode
0x0ebc - EFI byte code
0x014c - Intel 386 or later processors and compatible processors
0x0200 - Intel Itanium processor family
0x9041 - Mitsubishi M32R little endian
0x0266 - MIPS16
0x0366 - MIPS with FPU
0x0466 - MIPS16 with FPU
0x01f0 - Power PC little endian
0x01f1 - Power PC with floating point support
0x0166 - MIPS little endian
0x01a2 - Hitachi SH3
0x01a3 - Hitachi SH3 DSP
0x01a6 - Hitachi SH4
0x01a8 - Hitachi SH5
0x01c2 - ARM or Thumb (“interworking”)
0x0169 - MIPS little-endian WCE v2

So to check if it is 64-bit, we need to look for:

0x8664 - x64
0xaa64 - ARMv8 in 64-bit mode
0x0200 - Intel Itanium processor family

And as Bob mentioned, here is a list of some more machine types (see 11 pg.), however it is not very likely to find them.

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Don't forget 0x0200 (Itanium). That would be IA-64, as opposed to x86-64 (AMD64). There's a couple more "64-bit" machine types possible, but you're very unlikely to find them in the wild (0x0284 is the 64-bit Alpha AXP, from the 1999 documentation, and not supported by Windows after NT4/2000RC). –  Bob Aug 8 '14 at 10:55
@Bob Thank, edited to include your info. –  ST3 Aug 8 '14 at 11:09
For a visual reference, image showing the location of the PE header with 0x8664 (highlighted): i.imgur.com/yHvcgdn.png (notepad++ hex-editor plugin) –  zamnuts Aug 8 '14 at 14:47
To quickly find the target machine value: Take the DWORD at offset 0x3C. Add four to this value. That is the offset of the Machine WORD. (Both are little endian) –  user1354557 Aug 25 '14 at 21:45
Where do you find 0xaa64 - ARMv8 in 64-bit mode? I have not such #define in winnt.h. –  SerG Feb 12 at 14:34

It's easier to check Magic of Optional Header.

For a valid exe, only two values are possible:

0x10B - PE32  - 32 bit
0x20B - PE32+ - 64 bit
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