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I develop (mainly UWP apps for personal enjoyment atm) on a x64 laptop, but in Visual Studio I have been blindly using the default x86 solution platform.

Should I be using x64 or x86? (so ashamed to even be asking)

There's a few previous questions that touch on the subject and mention differences at a high level but these don't really state any solid guidance as to when to use one over the other (noting that you could always perf test as you went and develop using the fastest).

What's so special about x64 and programming x86?

https://stackoverflow.com/questions/607322/what-are-the-advantages-of-a-64-bit-processor

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Adrian K
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  • I know you said it was UWP apps and not web apps, but I feel [this post](http://www.hanselman.com/blog/PennyPinchingInTheCloudYourWebAppDoesntNeed64bit.aspx) from Scott Hanselman still applies. tldr; Unless you know you need 64bit, you probably don't. – neilsimp1 Dec 09 '16 at 13:19
  • I just wasn't sure if UWP had any specific implications that it was worth knowing about for x64 vs x86. – Adrian K Dec 09 '16 at 20:29

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In practical terms, you would use X64 when:

  1. You need to directly address more than 4GB of memory, or
  2. You need very fast (native) processing of 64 bit numerical quantities (including double-precision floating-point numbers)

X86 (32 bit) is suitable for most everything else.

Robert Harvey
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    Hooray, simple advice for simple developers :) – Adrian K Dec 09 '16 at 03:12
  • or 3. when you want to use security features like Address Space Layout Randomization, NX bits, … or 4. when you want to use instruction set extensions, like vectorization, hardware-accelerated crypto, …. – amon Dec 09 '16 at 16:47
  • @amon: Well, yes, but the OP's question doesn't suggest exotic applications, and my answer isn't meant to be comprehensive, but only advisory. – Robert Harvey Dec 09 '16 at 16:49
  • @amon - I guess that if I ever start looking at anything where the bit size / chip architecture does have significant programming implications then the differences will become more real and understood - i.e. when they start to take on real meaning to what I'm doing. Robert Harvey correctly interpreted the OP - sorry if it wasn't so clear. – Adrian K Dec 09 '16 at 20:35