[bitcoindev] Testnet 4 difficulty/hashrate

[bitcoindev] Testnet 4 difficulty/hashrate

[Anthony Towns]

On Fri, Jun 05, 2026 at 07:35:27PM +1000, Anthony Towns wrote:
> compared with current mainnet difficulty of ~138T, or testnet4's 
> current difficulty of ~1239M,

If testnet4's current difficulty is D=1239M [0], and there were
no min-difficulty blocks, that would be one thing. But there are
min-difficulty blocks, and sufficient hashrate mining them with the clock
set forward to saturate them. What's the actual hashrate for testnet4
given a reported difficulty D?

[0] https://mempool.space/testnet4/block/000000000000000359f805aea2a5f18671bf98a1106d0cdbbfbe1f341f5e08dc?showDetails=true&view=actual#details

Suppose the "correct" difficulty corresponding with actual hashrate would
be H.  Then real difficulty blocks are found every (D/H * 10 minutes)
on average, and minimum time blocks fill up the rest of the retarget
period. So between blocks 135072 and 137087, I see 192 real-difficulty
blocks and 1824 min-difficulty blocks, suggesting that the real testnet4
difficulty should be H=130M.

The limit on not having D/H=2016 is that with 2016 min-difficulty blocks,
you'd have a retarget period taking up 4 weeks instead of 2 weeks. I think
a real-difficulty block can reset up to 5 or 6 blocks of min-difficulty
time (any more than that would violate median time constraints on behalf
of the real difficulty block, or too-far-in-future constraints on the
min-difficulty blocks), so I think that means that you want at least
1 real block for every 10 or 12 min-difficulty blocks, so a 192:1824
(1:9.5) ratio seems close to the max already.

This also suggests ~90% of testnet4 blocks are being confirmed via
competition in network propagation with only ~10% confirmed via
PoW/hashrate competition.

Cheers,
aj

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[bitcoindev] Re: Testnet 4 difficulty/hashrate

[Ali Sherief]

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This is having consequences in development workflows. Tests with 
bitcoin-related libraries with this kind of block generation is now almost 
impossible unless you mine your old blocks. For instance, my testnet4 
faucet transactions have been sitting in the almost-empty mempool for 
around 30-60 minutes, never confirm, and then drop out.

It is certainly making developing Bitcoin-related stuff much harder

-Ali

On Friday, June 5, 2026 at 1:28:01 PM UTC+3 Anthony Towns wrote:

> On Fri, Jun 05, 2026 at 07:35:27PM +1000, Anthony Towns wrote:
> > compared with current mainnet difficulty of ~138T, or testnet4's 
> > current difficulty of ~1239M,
>
> If testnet4's current difficulty is D=1239M [0], and there were
> no min-difficulty blocks, that would be one thing. But there are
> min-difficulty blocks, and sufficient hashrate mining them with the clock
> set forward to saturate them. What's the actual hashrate for testnet4
> given a reported difficulty D?
>
> [0] 
> https://mempool.space/testnet4/block/000000000000000359f805aea2a5f18671bf98a1106d0cdbbfbe1f341f5e08dc?showDetails=true&view=actual#details
>
> Suppose the "correct" difficulty corresponding with actual hashrate would
> be H. Then real difficulty blocks are found every (D/H * 10 minutes)
> on average, and minimum time blocks fill up the rest of the retarget
> period. So between blocks 135072 and 137087, I see 192 real-difficulty
> blocks and 1824 min-difficulty blocks, suggesting that the real testnet4
> difficulty should be H=130M.
>
> The limit on not having D/H=2016 is that with 2016 min-difficulty blocks,
> you'd have a retarget period taking up 4 weeks instead of 2 weeks. I think
> a real-difficulty block can reset up to 5 or 6 blocks of min-difficulty
> time (any more than that would violate median time constraints on behalf
> of the real difficulty block, or too-far-in-future constraints on the
> min-difficulty blocks), so I think that means that you want at least
> 1 real block for every 10 or 12 min-difficulty blocks, so a 192:1824
> (1:9.5) ratio seems close to the max already.
>
> This also suggests ~90% of testnet4 blocks are being confirmed via
> competition in network propagation with only ~10% confirmed via
> PoW/hashrate competition.
>
> Cheers,
> aj
>
>

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