I will be traveling from Pakistan to Slovenia by business visa (short term Schengen). I will be traveling from Pakistan to Istanbul and from Istanbul to Ljubljana (Slovenia). Do I need to get Istanbul transit visa? I need information for both cases i.e going outside of the airport or staying inside the airport. I'm traveling for the first time and I am a Pakistani Citizen.
If you don't leave the airport then you do not need a visa.
If you plan to leave the airport you will need to apply for an eVisa from the Turkish government from : evisa.gov.tr as they no longer provide visas upon arrival.