Many students have confusion before giving any English proficiency test. IELTS and TOEFL both exams are recognized worldwide and also widely accepted.
only the difference is that
TOEFL is an internet based test so known as TOEFL - iBT and mainly accepted by many universities in USA and in some other parts of the world. ETS conducts and assesses this test. This body is a private nonprofit organization devoted to educational measurement and research, primarily through testing. For further information you can log in http://www.ets.org
IELTS is a mainly pen and paper based test governed by Cambridge University's ESOL examination Board,British Council and by Australia's IDP Education Centre. The result of this exam accepted in English speaking nations mainly who welcome foreign students, professionals or immigrants especially CANADA, AUSTRALIA, NEW ZELAND, UK and other parts of European countries. For further information you can log in http://www.ielts.org/
However IELTS is also accepted in USA in many number of universities including Yale or Massachusetts even.