What's the difference between IELTS and TOEFL?

TOEFL (iBT) is generally accepted in American universities, although it is also accepted in many other schools across all continents. The test had its own Extreme Make Over!

Now TOEFL is also getting competition, and the competition has set off debates at American colleges over the best way to measure students’ English competency, the obligations of American colleges to students from the poorest parts of the world, and the changing nature of international recruiting.

The challenger to TOEFL is the International English Language Testing System, known by its acronym, IELTS. Co-sponsored by the English testing entity of the University of Cambridge, and British and Australian organizations that encourage international education, IELTS has long been the dominant test for students from non-English speaking countries seeking to enroll in English-speaking nations of the British Commonwealth. But in the last three years, IELTS has quietly become a force in the United States as well, where the number of colleges accepting IELTS on equal footing with TOEFL has doubled, to more than 800.
IELTS is generally accepted in the UK, Australia and other countries from the Commonwealth. IELTS has gained popularity and acceptance in many universities beyond the UK.