What IELTS score do you need for Bielefeld University?

The World Studies page notes that many certificates have a validity period of two years and says certificates from university language centres or language schools are not accepted, only internationally recognised ones. It accepts a confirmation of English as the language of instruction for your whole undergraduate degree, and a German Abitur where no specific certificate exists.

The Behaviour page waives proof for native speakers and for a first degree from an English-speaking institution. The Data Science page waives it if your entrance qualification or an English-language degree came from Australia, Ireland, Canada, New Zealand, the UK or the USA, and does not require German.

The British and American Studies figure comes from the language requirements page, where it is listed as an exception to the B2 rule. If you are applying to one of the other B2 programmes, open its page and look for the IELTS line before you book, since the main page names no band for them.

Requirements vary by programme and change between admissions cycles. The score that binds you is the one on your Bielefeld programme page and in your offer letter, so check it there before you book a test.