Any difference between onus and responsibility?

mostly, i see the word responsibility. When do people use onus and can we just use responsibility? Are there any special meaning?

‘Responsibility’ is by far the more common of the two. Besides, ‘onus’, which is rather formal and definitely not an everyday word, has the sense of responsibility for a difficult task.

They’re used differently, too, at least the way I see it and hear it

That’s their responsiblity. The onus is on them.

For everyday tasks, they are my responsibility. I would never say “the onus is on me to get that report distributed” but I could say "it’s my responsiblity to get that report distributed.

thank you very much.