I'd like to use the Polkadot CLI to create a chainspec with specific user balances pre-seeded. I'd like to be able to do this for any of the dev runtimes.

In the case of the polkadot dev runtime, I run polkadot build-spec --dev. In the case of others, I run polkadot build-spec --chain=<runtime-name-here>-local. I capture the output in a file, and then overwrite its genesis.runtime.balances.balances with a list of [ss58, amount] tuples.

Then I write the updated chainspec to my fs, and run it with polkadot --chain <path-to-spec>. In the case of Westend, I'm able to retrieve a test user balance. All others fail. Also, westend txs stall.

  • Hi Harry, are you getting the raw version after you update the genesis file?
    – pepoviola
    Jan 29 at 20:53
  • For future readers: we attempted to create a raw version from the edited, and still ran into the same issue. Will follow up if/when it's resolved. Feb 5 at 21:04

1 Answer 1


Achieved in Capi's devnet spawning logic like so.

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