I'm trying to get in on some ICO's, and was wondering what the best way to get in was using Parity. I've read some people say that you should use n-2 so the block number the ICO starts at minus two blocks to ensure you get in right at the block start.

But I've also read this doesn't work anymore. I've read to put n-1, 1 block less as well. Can someone who has knowledge in this tell me what the best block to send at is to ensure I'm one of the first one's at the starting block?

Thank you.

1 Answer 1


If you want to get your transaction into the block n, you would have to broadcast it at block n - 1.

Here is what roughly happens, I use block 100 as an example:

  • You schedule a transaction to be sent at block 100 with Parity.
  • Parity waits until it receives block 99 and broadcasts your transaction.
  • Miners are already working on block 100 and now receive and acknowledge your transaction. But they wont include it in 100 because that block is already prepared to be sealed.
  • Miners seal block 100 and start working on block 101. Since they are aware of your transaction by now, there is a chance they include it in 101 - but not earlier.

However, if the network is congested, it's very likely that your transaction will be pending till 103, 107 or 186. That mainly depends on your selected gas price and how many users are willing to spend even more on fees.

TL;DR if you want to get into block n = 100, then you will have to broadcast at n - 1 = 99.

  • Your latest revision doesn't look internally consistent. Based on your step-by-step explanation, I'd conclude that you would have to broadcast at n - 2, however that isn't your conclusion.
    – J-B
    Commented Jun 20, 2017 at 14:06
  • 1
    @JorisBontje If you put it in at n - 2 there's also a good chance that you'll send it too early and have it rejected.
    – Arrisar
    Commented Jun 20, 2017 at 14:35
  • @JorisBontje if you schedule it for 100 it wont get in earlier than 101. If you schedule it for 99 (n - 1), it could get into 100.
    – q9f
    Commented Jun 20, 2017 at 18:05

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