Are tinned prunes kosher?

Not sure I understand your question, but as are many foods, some prunes are kosher, some not. Here are some that are kosher_

Just an Aunty’s point of view (and a prune lover), but I think that for any food to be properly Kosher, it has to have been blessed or spoken over by a Rabbi. This should be written somewhere on the label, most kosher foods are notified. Hope they taste as good as the ordinary ones!

The issue is not the prunes themselves, but the utensils used to cook them. Any utensil used in the preparation of non-kosher food and then used to prepare an otherwise kosher food (like the prunes) would render them non-kosher (unless they are purified according to set procedures). The facilities and utensils would have to be certified kosher for the product to call itself kosher.

@thorninmud is correct.

Probably more than you ever wanted to know about kashruth. Around the eighth paragraph there is a discussion of fresh and canned fruit. Of course, your rabbi may vary.

@auntydeb Blessing is not part of the kosher-certification process.