Can IELTS be an alternative to TOEFL?

Yes and no. Both IELTS and TOEFL are designed to assess test takers’ English language proficiency for academic and communication purposes. Although the formats of the two exams are similar, there are also many differences. You can take the TOEFL or IELTS exam if the college or university (or other organization that requires a certificate) that you intend to attend accepts either. If they have any strict requirement that you have the TOEFL, your IELTS certificate will not be accepted, and vice versa.

In practice, most colleges, universities, and immigration authorities accept both of these exams.

It is common knowledge that US universities prefer TOEFL results, while European and other universities accept IELTS. A long time ago, the US agreed to recognize IELTS in addition to TOEFL and accept both certificates for applicants. However, there are some institutes and universities that do not accept IELTS and insist on passing TOEFL. For an up-to-date list of universities accepting IELTS, please visit https://www.ielts.org/

Before taking an exam, always check and verify which exam and module (Academic / General) the organization or institution requires.