On April 8, 2025, at 12:19 UTC, Bitcoin Cash (BCH) underwent its first block reward halving, reducing miner rewards from 12.5 BCH per block to 6.25 BCH. This milestone, triggered automatically at block height 630,000, marked a pivotal moment for the network — but one followed by an immediate exodus of mining power.
Miners don’t operate for free. Running thousands of mining rigs requires significant investment in electricity, hardware maintenance, and operational logistics. With the halving cutting their income in half overnight, many operators faced tough decisions: shut down unprofitable machines or migrate to more lucrative blockchains.
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Immediate Impact on BCH Hash Rate and Network Security
According to data from CoinWarz, shortly after the halving, both the difficulty and hash rate of the Bitcoin Cash network began a steep decline. The hash rate — a measure of computational power dedicated to securing the blockchain — plummeted from a peak of 4,001.5 petahashes per second (PH/s) on April 8 to just 785 PH/s, representing an 80% drop.
At the same time, network difficulty — the dynamic metric that adjusts how hard it is for miners to solve blocks — fell nearly 50%, dropping from 528 billion to 269 billion. This dual collapse raised serious concerns about the network's security.
Security analyst Kyle Torpey from LongHash had previously warned that BCH would face increased vulnerability following its first halving. These fears were quickly validated.
Data from Crypto51.app, which estimates the cost of launching a 51% attack on various blockchains, shows that as of April 13, 2025, at 16:30 Beijing time, it would cost only $9,121** to attack the BCH network for one hour — equivalent to about 41.11 BCH at current prices. In contrast, attacking Bitcoin would cost approximately **$520,000, over 57 times more. Even Ethereum, with an hourly attack cost of $85,377, remains significantly more secure than BCH.
These figures are derived from the cost of renting enough hash power via platforms like NiceHash to control over half of a network’s total computational strength. While NiceHash itself may not have sufficient capacity to execute such attacks in practice, its pricing provides a useful benchmark for assessing relative blockchain security.
A successful 51% attack allows malicious actors to manipulate transaction history — including reversing or double-spending transactions. This poses a direct threat to exchanges and custodial services, where attackers could deposit coins, trade or withdraw assets, then reverse the original transaction, effectively stealing funds while retaining both the coins and the acquired value.
BSV Halving Follows Similar Pattern
Just two days later, on April 10 at 20:48 Beijing time, Bitcoin SV (BSV), another Bitcoin fork known as "Satoshi’s Vision," experienced its own halving event. Miner rewards dropped from 12.5 BSV per block to 6.25 BSV — again, a 50% reduction in income.
As with BCH, the effect was swift and severe.
In the 24 hours preceding BSV’s halving, BCH had already shown signs of instability, losing up to 80% of its hash rate and seeing difficulty fall by 50%. BSV followed a similar trajectory.
BlockChair data reveals that BSV’s hash rate declined from 3.06 exahashes per second (EH/s) before the halving to 1.83 EH/s by April 13 — a 40% decrease. Meanwhile, network difficulty dropped from 420 x 10⁹ to 212 x 10⁹, according to satoshi.io.
Perhaps more telling was the slowdown in block production: within 15 hours post-halving, only 35 blocks were mined — 55 fewer than expected under normal conditions. Blockchains are designed to produce blocks at regular intervals (about six per hour for BSV), with difficulty adjusting dynamically to maintain this pace. The sharp drop indicates a sudden loss of active miners.
Why Hash Rate and Difficulty Drop After Halving
The root cause lies in miner profitability.
With block rewards halved and no immediate increase in token price or transaction fees, many mining operations — especially those running on thin margins — become unprofitable. As a result, miners power down rigs or redirect their hash power to more rewarding networks.
This migration reduces the number of computers validating transactions, slowing down block creation and increasing confirmation times. It also weakens network security by lowering the total computational effort required to overpower the chain.
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Market Reaction and Recovery Trends
Following the initial shockwaves, both BCH and BSV have seen partial recovery in hash rate and difficulty. However, as of mid-April 2025, neither network has returned to pre-halving security levels.
Meanwhile, Bitcoin’s hash rate has continued to climb — suggesting that displaced miners are flocking to BTC mining instead. This trend underscores a broader reality: in a competitive mining economy, capital follows profitability.
Notably, BSV’s price has lagged behind BCH, currently trading nearly $40 lower, further discouraging investment in its ecosystem.
Core Keywords:
- BCH halving
- BSV halving
- hash rate drop
- block reward halving
- mining profitability
- network security
- 51% attack risk
- Bitcoin Cash mining
Frequently Asked Questions
What is a block reward halving?
A block reward halving is a programmed event in many proof-of-work cryptocurrencies where the amount of new coins awarded to miners for validating blocks is cut in half. It typically occurs at set intervals (e.g., every 210,000 blocks for Bitcoin) to control inflation and mimic scarcity.
Why does hash rate drop after a halving?
After a halving, miner income drops by 50% overnight. If the coin’s price doesn’t rise accordingly or transaction fees remain low, many miners operate at a loss. This forces less efficient operators to shut down or switch to more profitable chains, reducing overall network hash rate.
How does lower hash rate affect security?
A lower hash rate makes a blockchain more vulnerable to attacks — particularly 51% attacks — where an entity gains majority control over mining power and can manipulate transaction records. Networks with significantly reduced hash rates become cheaper targets for such exploits.
Are all halvings this disruptive?
Not necessarily. The impact depends on market conditions. For example, Bitcoin’s halvings have historically been preceded by bull runs that offset income loss with rising prices. In contrast, BCH and BSV lacked similar momentum in 2025, amplifying the negative effects.
Can network difficulty adjust fast enough?
Yes — most blockchains automatically adjust mining difficulty every few days (or even every block) to stabilize block production. However, rapid hash rate fluctuations can still cause temporary delays in transaction processing until equilibrium is restored.
Is mining still profitable after halving?
For well-capitalized miners with access to cheap electricity and efficient hardware, mining can remain profitable — especially if they anticipate future price increases. But smaller operators often struggle unless external factors (like rising prices or fee income) compensate for reduced rewards.
While halvings are built into cryptocurrency protocols as mechanisms for supply control, their real-world impact hinges on economics and miner behavior. The 2025 BCH and BSV halvings serve as case studies in how weaker networks can face severe strain when incentives shift suddenly.
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