There are many exams to prove your level of English. The choice of exam depends on the goals of the individual student.

Currently IELTS, TOEFL, Cambridge exams are very popular.
IELTS - International English Language Testing System
The main advantages include:
- the frequency of the exam. In large cities it is held every week, in the rest at least once a month.
- the opportunity to pass the exam with any level of English. It doesn't matter if you speak English at level A2 or C2 - you will take the same exam and, based on the results, you will receive a certificate confirming one or another level.
- widespread use. This certificate can currently be used for employment abroad if it is necessary to confirm the level of the language, for migration, for admission to the university (you need to select the Academic version).
TOEFL - Test of English as a Foreign Language
The main difference between TOEFL and IELTS is that the former is more common in North America (in the USA and Canada), but now more and more organizations accept both exams as equivalent.
Cambridge exams
Designed for five levels of difficulty - from Pre-Intermediate to the level of a native speaker. There is also a separate series of exams for children.
The main features are:
- strict exam dates: usually 3 times a year
- the obtained certificate is valid for life and does not require retaking after the expiration of time
- The exam assignments correspond exactly to the level assessed, but there is a possibility that the scores won will not be enough to confirm the specified level, and the examinee will not receive his certificate.
Of course, the cost of exams is also different:
- the cost of IELTS in Russia currently ranges from 14,000 rubles
- TOEFL - $ 260
- Cambridge exams - from 7,500 to 14,000 rubles, depending on the level.