Web3 & DApp Development Fundamentals · Lesson

Finality and Forks

Chain agreement.

When Is a Block Final?

Adding a block is not the same as it being permanent. Finality is the guarantee that a block can no longer be reverted.

Understanding finality and forks is key to knowing when a transaction is truly settled.

A fork occurs when the chain temporarily splits into two competing branches — for example, when two valid blocks appear at nearly the same time.

The network must decide which branch becomes the official history.

Block 9
   |
   +-- Block 10a (branch A)
   |
   +-- Block 10b (branch B)
Which one wins?