How to tell if binary is x86 or amd64?

First get dumpbin tool, ships with any Windows SDK. Run dumpbin /headers on the binary, then look at the magic number. This is an amd64 binary:   c:\>dumpbin /headers c:\amd64\msvcr100.dll | findstr magic              20B magic # (PE32+) This is a 32-bit binary:   c:\DPMedusa1>dumpbin /headers c:\x86\msvcr100.dll | findstr magic              10B magic # (PE32)…

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