I'm currently working to gain a deeper understanding of blockchain technologies, specifically in the context of parachains and relay chains, as well as solo chains. I'm having some confusion regarding the concept of a "best block" and how it operates in these different chains. I'd greatly appreciate a detailed explanation.

  1. Parachains and Relay Chains: Could someone please explain what the term "best block" means in the context of parachains and relay chains? How does this concept operate in practice? What is its significance for the network's operation and security?

  2. Relay Chain's Role: I understand that the relay chain plays a central role in maintaining consensus across parachains. How does the "best block" on the relay chain impact the state of all connected parachains? How often does this "best block" change?

  3. Solo Chains: I've also heard about "solo chains," but I'm unsure of their relevance and how the concept of a "best block" applies to them. Could someone provide some insight into what solo chains are and how "best blocks" work in this context?

  4. Use Cases: If possible, please provide some real-world examples or use cases where understanding the "best block" in these different types of chains is important.

I'd be grateful for any detailed explanations, references to official documentation, or examples that can help clarify these concepts. Thank you for your assistance in unraveling these intricacies.

1 Answer 1


In order to determine whether the new block is our new best:

  • Find the common ancestor between the current best and the new block's parent.
  • Count the number of Babe primary slot claims between the common ancestor and the current best.
  • Count the number of Babe primary slot claims between the common ancestor and the new block's parent. Add one if the new block has a Babe primary slot claim.
  • If the number for the new block is strictly superior, then the new block is our new best.

For algorithms other than Babe, all blocks simply count as one, such that the longest chain is the preferred one. Therefore, it is not meaningful to compare the score of an Aura chain and the score of a Babe chain.

  • First of all, I wanted to say thank you for your initial response – it's much appreciated. Being a newcomer to the Polkadot network, I'm genuinely eager to learn more. Could you kindly provide a thorough explanation of each of these steps and their role in determining the 'best block'? If possible, I'd also love to have access to any code examples or be directed to official Polkadot documentation to help me grasp the process better. Your guidance and assistance mean a lot to me, and I want to express my gratitude in advance for your response. Oct 25, 2023 at 5:09

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