No, IELTS is not mandatory for UK immigration. However, you must prove your proficiency in the English language through other standardized English language tests.
Although the IELTS is a popular English language test for UK immigration, candidates can also take the following alternative tests:
- TOEFL iBT Test
- Pearson PTE Academic Test
- The Occupational English Test (OET)
- The Cambridge C1 & C2 Exams