Unable to start XAMPP Apache server on MacOS-Sierra

Simply goto your terminal and type:

sudo apachectl stop 

It'll ask for password. Enter your system password.

Go back to XAMPP control panel and start Apache. It should get started now.

Another related issue, which I faced caused Apache sever failure. And failure logs is :

[Sun Jul 30 12:43:58.747822 2017] [unique_id:alert] [pid 9188] (EAI 8)nodename nor servname provided, or not known: AH01564: 
unable to find IPv4 address of "MacBook-Pro.local" AH00016: Configuration Failed

To solve this :

1. Executed following command

   sudo -e /etc/hosts
   

2. Then, changed following entries

   127.0.0.1    localhost
   ::1    localhost
   

   to

   127.0.0.1    localhost MacBook-Pro.local
   ::1    localhost MacBook-Pro.local
   

I found the solution:

1. Make sure port 80 is not being used (Use Network Utility and scan for port 80. If you found any application using port 80, then kill it)

2. Open terminal and execute

   sudo apachectl stop 
   

   (ignore, if you get any error)

3. On the same terminal window execute

    sudo /Applications/XAMPP/xamppfiles/bin/apachectl start
   

4. Open XAMPP control panel, your apache server might have started by now, if not then you can start manually by clicking start button.

This worked for me!!

I had the same Problem and fixed it by deleting the lib folder in Applications/XAMPP/xamppfiles/ and installing XAMPP again. It's probably due to old lib files from previous versions not being updated properly.