Can converting NFA to DFA change the language? In the context of studying the conversion from an NFA to the equivalent DFA, I came across the following NFA, which accepts all strings over the alphabet $\{0,1\}$ which contain $01$:

After I converted the NFA to the equivalent DFA, it became:

The issue is that the NFA accepts the string $101$ but the DFA doesn't.
Is my conversion wrong or is there something I am missing about the NFA to DFA conversion?
By definition, two automata are equivalent if they accept the same language.
In your case, the DFA you construct is indeed equivalent to the NFA you start with. Both of them accept all strings starting with $01$. In particular your NFA does not accept $101$.