Is 'Kudos' an informal word?

I found some references that were telling that it's an informal word. Can I use it in formal language, for example in IELTS speaking test?

1 Answer
Feb 3, 2017

Kudos is informal

Explanation:

Kudos is informal. But it might be good to use in response to an informal question. Perhaps if the prompt is informal (Ex. "Who's your favorite basketball player?") then you could use it, but if the prompt is formal (Ex. "Tell me your business proposal to maximize profit") then you would avoid it.

I recommend staying clear of the word altogether, and using synonyms like "respect/praise" or "congratulations".