#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "&redirect_uri=\S+?localhost\K%[^%]+"
Local $sString = "https://www.facebook.com/v2.5/dialog/oauth?client_id=*****&state=*****&response_type=code&sdk=php-sdk-5.1.2&redirect_uri=http%3A%2F%2Flocalhost%3A8888%2Ffacebook%2Flink&scope=email%2Cuser_birthday%2Cuser_photos"
Local $sSubst = ""
Local $sResult = StringRegExpReplace($sString, $sRegex, $sSubst)
MsgBox($MB_SYSTEMMODAL, "Result", $sResult)
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for AutoIt, please visit: https://www.autoitscript.com/autoit3/docs/functions/StringRegExp.htm