I am trying to a simple thing, just like that, in a header file;

#include <filesystem>
#include <iostream>
namespace fs = std::filesystem;

And IntelliSense goes: namespace std has no member filesystem.

Okay no worries, it's an easy fix. Just set the C++ language standard in the propery pages...

Well, it turns out it isn't, it's not an option in Unreal VS project. Tried typing in search bar, View -> Property pages, but no luck.

Okay let's try doing the whole thing in a console project first.

Same message from IntelliSense as before.

Ok, no worries, I found this.

I found my settings under: Project > projectname Properties

And voila, the console app works.

Let's try it in the Unreal project.

Well, well... My options are limited here.


I had a look around in the project settings as well:


How do I get this filesystem header work with my project?

  • \$\begingroup\$ Googling "ue4 c++17" gives me several different results with varying degrees of success from users, none of which seem to suggest changing this from VS or UE4 settings. \$\endgroup\$
    – user35344
    Commented Jul 2, 2020 at 10:56
  • \$\begingroup\$ What is it that you're trying to achieve in the end? It may be that there's no way to do this as you're trying to do it but Unreal may have a solution of its own that will work. \$\endgroup\$
    – Stephen
    Commented Jul 2, 2020 at 11:16
  • \$\begingroup\$ I am trying to load fbx files, and load the file structure tree into a string. Something like that: rosettacode.org/wiki/Walk_a_directory/Recursively#C.2B.2B Not sure if this is the "Unreal" way of handling files. \$\endgroup\$ Commented Jul 2, 2020 at 12:17
  • \$\begingroup\$ But for now, I would like to load/read files \$\endgroup\$ Commented Jul 2, 2020 at 12:20
  • 1
    \$\begingroup\$ My guess is that the downvotes are because your question doesn't show any attempt to implement the approaches Tyyppi_77 mentioned can be found with a search. Can you show us what happens when you try implementing these approaches? \$\endgroup\$
    – DMGregory
    Commented Jul 2, 2020 at 13:10

1 Answer 1


Okay, found the solution here.

CppStandard = CppStandardVersion.Cpp17;

I added this to my myproject.Build.cs

  • \$\begingroup\$ Make sure to close VS and in UE4 do File -> Refresh Visual Studio project Files after this change. This fixes the project settings for IntelliSense to work. \$\endgroup\$
    – javs
    Commented May 26, 2021 at 1:12

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