How can I prune my Bitcoin Core correctly? The other way did not work for me. Have I done any unnoticed mistake? Saving the entire blockchain in my computer is taking mi a lot of space. I looked in this forum for a solution and I saw that there was an option to prune the node and save a lot of space.
I followed the instructions, I went to the Bitcoin data directory, I created a file there and called it "bitcoin.conf" and I wrote "-prune=1100" in it.
Nothing I expected happened, the space it took remained the same, it only started downloading a new blockchain called "testnet".
Have I done something wrong? And how can I fix it in order to save space?
My version of Bitcoin Core is v0.14..2

PS: Latter, I have discovered that, in fact, I have three Bitcoin data directories, and suddenly I have doubts about in which of them shall I place my "bitcoin.conf".
Is having three directory data how it shall be? And in which of them shall I place my "bitcoin.conf".
From your description it sounds to me that you may have edited your configuration file while Bitcoin Core was already running.

prune=1100 is a startup parameter. It will take effect once you restart the program.


If you add a parameter to the startup instructions,  parameters start with a dash (-prune=1100), e.g.:

"C:\Users\&lt;username&gt;\AppData\Roaming\Bitcoin\bitcoin-qt.exe" -prune=1100


Please make sure you use the correct path for the actual directory you installed Bitcoin to.
If you add it to the configuration, the parameter must be listed without a dash in the bitcoin.conf:

prune=1100


If you're unsure how to locate your Bitcoin data directory, please see: Where is the configuration file of Bitcoin-Qt kept?


There is no need to manually delete any files from your Bitcoin directory, or to start over the initial blockchain download to enable pruning.
You merely need to restart Bitcoin Core after you've edited the bitcoin.conf. If you don't know how to restart a program, you may find it simpler to shut down and restart your computer.