Difference between に違いない and に間違いない I'm familiar with the construct: > _sentence_ \+ > surely/must be/no doubt that _sentence_ So in the sentence > > The contents must surely be of the cake or baked sweet kind (my translation). I'm assuming that **** plays the same role. What is the difference between these constructs? My gut tells me that shows more certainty that , but my gut is very unreliable when it comes to Japanese.

According to this thread it seems to me that the majority of the answers say that is a stronger version of , while is closer to a personal "sureness". I'll paraphrase some of the answers for convenience.

According to the top answer, means that the speaker came to a conclusion and is very sure that it is correct, but it is ultimately their own opinion. There is a little uncertainty, but the speaker is very confident in what they are saying.

is described as a 100% certainty that there is nothing wrong with the statement. It seems to describe a personal conclusion as well, but is a bit more objective.

One of the other answers explains it like this:

> ?
>

So, .
I don't know if there is a maybe more nuanced difference between the two, but this seems to be the general agreement on the internet. Some other sites like this HiNative page say similar things.