Xdebug port is occupied by built-in web server in PhpStorm: unable to receive debug connections

Problem 

• Xdebug is configured correctly, but it doesn't establish a connection.

• Validation script from Settings | PHP | Debug provides the error below:

  PhpStorm: unable to receive debug connections

Cause 

Xdebug port is occupied by the Built-in Web Server.

The following messages can be found in the idea.log:

INFO - #o.j.i.SubServer - Built-in sub-server 'BuiltInServerOptions$MyCustomPortServerManager' started on port 9003

or

INFO - #c.i.e.r.ExecutionUtil - Error running 'Sym Bug':<br>Port 9003 is busy
com.intellij.execution.ExecutionException: Port 9003 is busy
	at com.jetbrains.php.util.connection.PhpIncomingDebugConnectionsServerSocket.openConnection(PhpIncomingDebugConnectionsServerSocket.java:23)

Resolution 

Depending on the PhpStorm version:

• For 2025.2 and later:

  1. Open Settings | Tools | Web Browsers and Preview.

  2. Set the default value '63343' under the Built-in Server section.

  3. Apply changes.
   

• For 2025.1.x and earlier:

  1. Open Settings | Build, Execution, Deployment | Debugger.

  2. Set the default value '63343' under the Built-in Server section.

  3. Apply changes.