I've been putting a small helper library together which I'm just including manually via the libraries sub-directory. I've just made some changes to the library in the filesystem however when trying to compile a previous sketch referencing it (after making the appropriate changes), the compiler is complaining and it appears to still be using the old version of the library. What's going on here and what is the correct way to update such a library?

I have tried completely reloading the Arduino IDE to flush out any caches etc. but that didn't help

  • 2
    rename the library file and see if the compiler complains that it cannot find it
    – jsotola
    May 7, 2020 at 16:41
  • The file path should be included in any error message from the compiler and that should tell you if it's really using the file you think. May 7, 2020 at 23:49

1 Answer 1


Whatever compiler you are using (Arduino IDE?) should have a 'verbose' setting that you can activate. This will give you a HUGE amount of output, but will also show you exactly what file is being accessed for the library in question.

When I do this, I copy/paste the entire output into Notepad++ and use its search capabilities to sort through all the chaff.


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