After all gives the idea that one thing was expected, but the opposite happened. It means ‘Although we expected something different’.
– I’m sorry. I thought I could come and see you this evening, but I’m not free after all.
– I expected to fail the exam, but I passed after all.
Position: usually at the end of the clause.
We can also use after all to mean ‘We mustn’t forget that … ‘ It is used to introduce a good reason or an important argument which people seem to have forgotten.
– It’s not surprising you’re hungry. After all, you didn’t have breakfast.
– I think we should go and see Granny. After all she only lives ten miles away, and we haven’t seen her for ages.
Position: usually at the beginning of the clause.