The short answer
Take IELTS Academic if you are heading to the UK, Australia, Canada or Europe: it is the most widely accepted and required for some visas. Take TOEFL iBT for the US. Duolingo is cheaper and faster and many universities accept it, but it does not work for the UK visa and not every programme takes it.
The main differences
- IELTS: a face-to-face speaking test and a score out of 9. Results in days for the computer version.
- TOEFL iBT: fully on computer, including speaking, scored out of 120.
- Duolingo English Test: taken at home in about an hour, results in two days, at a much lower cost.
Mind the visa rules
A university accepting a test does not mean the visa does. The UK requires an approved test (a SELT) such as IELTS for UKVI for courses below degree level, such as a foundation year. Ask before you book.
When to take it
At least three months before you apply, so there is time for a retake. Scores are valid for two years.