I understand that Ethereum PoS will have validators that proposes blocks (instead of miners that mines blocks).

IN all the description I am reading I am also coming across something called crosslink, which I do not understand at the moment.

What exactly are cross links? how do they fit into the contents of the blocks minded by validator? Are they related to shards? if so, does that means no crosslinks until sharding is added to ethereum? Thanks.

1 Answer 1


Try this

A crosslink is a reference in a beacon block to a shard block. A crosslink is how the Beacon Chain follows the head of a shard chain. As there are 64 shards, each beacon block can contain up to 64 crosslinks. A beacon block might only have one crosslink, if at that slot, there were no proposed blocks for 63 of the shards. Crosslinks are planned for eth2 Phase 1 to root the shard chains into the Beacon Chain, serving as the base of the shard fork choice, shard chain finality, and for cross shard communication. All shard chains are following the Beacon Chain at all times.

Crosslinks are basically pointers to shards from the main chain. When a successful shard block is to be added, a crosslink is created from the chain and only then the block can be part of the canonical history of the chain.

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