Super slow compiles on "powerful" machine!

Hello good internet folk:

I have been using arduino since version 1.0.1, and I have never really experienced any issues with compile times on several different machines. Right now I have a sketch of about 600 lines using the FastLED library version 3.001.003 which I know works perfectly fine. When I compile+upload from my 5 year old lenovo laptop, the whole process takes about 50 seconds. The aforementioned computer runs win10 latest update with a dual core i7 3520m and 4GB of RAM.

However, when trying the same sketch with my gaming machine (quad core i5 6600k 16GB RAM and also win10) compiling alone takes around 3 minutes! Both machines are running arduino 1.8.0, and I had the same issue with 1.7 and 1.6. Does anyone know what is going on? Any suggestions will be most appreciated.


Slow compiles under Windows
Add the Arduino directories to your antivirus / anti malware / other security exclusions.

So that would be at least two of the following.

C:\Program Files (x86)\Arduino
C:\Users\yourname\AppData\Local\Arduino15 depends on IDE
C:\Users\yourname\AppData\Roaming\Arduino15 depends on IDE

If you have your sketches set up in a different location it’s also worth adding that directory to the exclusions also.

Additionally if you also use the online IDE “CREATE” the following directories.


If you have installed to a different drive swap the drive letter as needed.
If you also have an unzipped IDE installed that path should also be added to exclusions

BTW only 4 GB ? seems quite low for a high end m/c

Oh and 1.7 is from not here (yet)

@Ballscrewbob Thanks for the advice I will try it tomorrow. It seems odd though, because both my laptop and desktop run spybot as my security software.

PS my old laptop is the one with 4GB RAM, my desktop has 16GB

Additionally you may want to try part of the Arduino clean up routine attached.

Just pick the clean up sections.


During compilation the IDE creates a bunch of files in the temporary build folder. This is located at C:\Users{user name}\AppData\Local\Temp{random build folder name}. So if the antivirus has to scan each of those files it could slow it down significantly. Since the build folder name is different every time(something like arduino_build_788025) it might be difficult to whitelist it in your antivirus software. You might temporarily disable your antivirus for one compilation to determine if it's the cause of the slowness.