Continuity mistake: When Jack holds the chain to Elizabeth's neck, and subsequently swings about, there are approximately ten links between the wrist shackles. When he tosses the links over the rope, before he slides down, there are at least fifteen attached links. Then at the blacksmith shop, when Jack sits at the anvil, there are eight links, and after he breaks it there are three links dangling from the right shackle and seven dangling from the left, totaling ten. (00:19:50)

Pirates of the Caribbean: The Curse of the Black Pearl (2003)
Ending / spoiler
Directed by: Gore Verbinski
Starring: Johnny Depp, Keira Knightley, Geoffrey Rush, Jonathan Pryce, Orlando Bloom, Jack Davenport, Mackenzie Crook
The pirates eventually have all of the gold returned, Cap'n Jack kills Barbossa, and Elizabeth agrees to marry the Commodore. Will confesses his love to Elizabeth, saves Jack from execution, and wins Elizabeth over. Jack escapes and returns to captain the Black Pearl. Watch after the credits and see that the monkey, Jack, has survived. He swims into the treasure cave, takes a piece of gold out of Cortez's chest and becomes a skeleton again...
yayee429
Trivia: Johnny Depp uses the phrase "Interesting..." as his trademark in many of the movies he stars in, including Sleepy Hollow. He uses it in PotC when Koehler's skeletal hand tries to grab him in prison.





Answer: The curse needs the blood of everybody who took a coin from the chest. All the other pirates have already contributed so, as the movie opens, the only blood needed is Will's, substituting for his father. During the finale of the movie, Jack takes a coin from the chest, adding himself to the curse, so his blood is now required as well as Will's.
Tailkinker ★
But I didn't see any blood on the coins, and none of the pirates cut themselves, even before Will became part of the mix.
Yes, the other pirates did cut themselves before Will came into it, off-screen. The lack of blood on the coins can simply be explained as most of it dripping to the bottom of the chest, it being washed away by storms blown into the cave, or by the fact that they didn't drop that much blood on it in the first place.
When they had Elizabeth they believed she was Bill Turner's daughter, but they all thought the curse had failed, none of them had cut themselves so it makes zero sense.
They had been collecting back the coins for years. During that time they repaid their own blood. All they needed was the last coin and the blood of Bill Turner to break the spell.
lionhead