Students often ask about the differences between these two tests. That is quite a hard question, because without more context the answer can vary. At a very high level TOEFL and IELTS are not that different. They both test your English proficiency in an academic setting and they test advanced English. So if you score well on the TOEFL, then you will probably score well on the IELTS. However, there are some big distinctions between the tests in the details.
British vs American
The first and most obvious difference is British versus American English. IELTS is a British test and as such uses British English. But what is more important to note is that IELTS is accepted by British universities. Some British schools also accept TOEFL, and some American schools – IELTS. The more important thing for you is to find out which test your desired school accepts.
Mechanical test differences
For example, the TOEFL has you talk into a microphone. In the IELTS you are required to speak with a real-life person. So that can really change your attitude towards the test because you could become really nervous when you’re speaking to another human being in English.
Another major difference is in the Listening sections of the two tests. IELTS listening is quite short, whereas TOEFL listening can be very long and it has more questions. So for the TOEFL your memory and your notes are extremely important, especially because you get the listening first and then the questions. On the IELTS you get the listening and the questions at the same time, so you don’t need to remember anything or take any notes.
Another difference is typing versus handwriting. The TOEFL has you type on a computer and IELTS has you write by hand. If you’re a very slow hand writer because you only ever type on a computer, then the TOEFL might be better for you.