How does Cumulus relate to Polkadot? What is the difference between the two?

Can I launch a chain without Cumulus? Are there any good documentation around the interactions between the two?

1 Answer 1


Probably an oversimplification, but you can think of Cumulus as a set of tools which allows you to convert a solo-chain Substrate blockchain into a Polkadot compatible Parachain.

More specifically, it provides libraries for all of the necessary parts of the Polkadot protocol necessary for Parachains to work, for example:

  • Creating new parachain blocks via Collators
  • Listening to the relay chain for updates
  • Synchronizing upgrades between the parachain and relay chain
  • etc...

These are all parts that are specific to being a parachain, so all of those things exist in the separate Cumulus repository, while Substrate focuses on just the general development of blockchains, independent of the Polkadot Protocol.

  • 1
    It should be said that unless you're switching out the consensus mechanism, then it's usually not too hard to turn a self-sovereign substrate chain into becoming a parachain.
    – Squirrel
    Feb 8, 2022 at 22:14
  • Is it therefore fair to say that i start with substrate and when the time comes I add cumulus or do I run into problems if i don't start with cumulus from day 1?
    – shredding
    Oct 26, 2022 at 18:43

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