I read an article about the delay of the difficulty bomb and understand reasonably well how the difficulty bomb will lead to longer and longer block times.

But it’s still not clear to me what will actually trigger the merge. I skimmed through the geth source code but couldn’t find a merge block number or merge terminal difficulty.

1 Answer 1


When a block is mined with a total difficulty equal to or exceeding the Terminal Total Difficulty (TTD), this will signal the Proof of Stake consensus to take over block production.


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In MainNet, the TTD is 58_750_000_000_000_000_000_000.

Here's a search term for Geth: https://github.com/ethereum/go-ethereum/search?q=TerminalTotalDifficulty

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