Who pays for Bitcoin’s security when the block reward is almost gone?

[Princeemmanuel070]

Everyone here knows the block reward gets cut in half about every four years, and most people see the halving as a good thing for the price, but here is the thing, I think the more important question is what happens to security when the subsidy becomes small. Right now miners are paid mostly by the new coins in each block, and fees are only a small part of that. That works today, which means that nobody feels the problem yet, but the subsidy goes down every cycle and at some point fees have to carry most of the cost.

I don’t think it is a disaster, because the market has time to adjust and miners can only spend what they earn, so hashrate will settle where it is profitable. Also, if Bitcoin is used more as a settlement layer, then fewer but bigger transactions can still produce a healthy fee market. But I also don’t think we can just assume it will work out, since there is no past example of a network this large running mostly on fees.

The risk I see is that low fee income means lower hashrate, and lower hashrate means a cheaper attack. It does not have to happen, but it is a trade off people should talk about before it becomes urgent. What do you think, will fees be enough on their own, or does Bitcoin need something else to keep miners paid?

[aoluain]

How is the security enabled and maintained at the moment?

Developers, Miners and Nodes!

At each halving all three groups continue to operate so when the halving events are
complete those 3 groups will remain.

This has already been factored into the algorithm and will be fine tuned as we near
the end of the halvings in about 100 years.

[JiiBs]

It’s is true that the block rewards for mining is greatly halved in every cycle, starting at 50BTC in its earliest days around 2009 to 2012 and later dropped to 25BTC by 2012 to 2016 and the trend continues to this day where it’s at 3.125BTC.

What’s worth noting through all these era is the value of Bitcoin.
In 2009 when Bitcoin didn’t have a defined price, people still mined probably because it did cost them nothing, haven’t done this from their desktop and at the comfort of wherever but, they did mined anyways. Then later on in 2010, Bitcoin has some valuation to it in cents and later a dollar and so on. On an average, the cost of a Bitcoin by 2012 was around $7-8 and miners still mined.

Then the 2012 to 2016 era saw that value rise to about $567 and if averaged across this time frame, we would find the price to be around $350-400 per Bitcoin.

While the number from block rewards might have dropped, the value of Bitcoin did appreciate. Today, those 3.125BTC is worth more than being rewarded with 25BTC in 2016 value wise when matched against eras.

In the eventuality that, miners don’t get block rewards no more, of course they would the rewarded from fees and the value for those sats would be worth the work put in and there would be a lot to be rewarded for since, the transaction might be massive at a global scale.

[_act_]

Do you know that miners are generating more on fees now than before?

The money generated on fees before 2020 were significantly below a billion United States dollars, but starting from 2021, miners generated more fees more than a billion United States dollars.

2023/2024 were the highest with a sharp decline in 2025, but still higher than the amount generated in 2022.

[Emjay24]

What do you think, will fees be enough on their own, or does Bitcoin need something else to keep miners paid?

Well, your title says "when the block reward is almost gone" and my simple reply to that is that the value of Bitcoin by then would've increased very well that the little sats would be worth much more than it is today, so it could be enough incentive to keep up the mining operation.

Going back to the direct question, miners would survive only on the fees when block reward is completely gone, although the fees might increase then. Less profitable miners would always exit and the ones that has access to cheaper electricity would remain. I don't think there would be a time there'll be deficiency of miners to secure the network.

[MusaMohamed]

Everyone here knows the block reward gets cut in half about every four years

More exactly, Bitcoin block subsidy halves every 210,000 blocks.
https://en.bitcoin.it/wiki/Controlled_supply

and most people see the halving as a good thing for the price, but here is the thing, I think the more important question is what happens to security when the subsidy becomes small. Right now miners are paid mostly by the new coins in each block, and fees are only a small part of that. That works today, which means that nobody feels the problem yet, but the subsidy goes down every cycle and at some point fees have to carry most of the cost.

Bitcoin miners care about rewards they get from each bitcoin block in $ value, and they don't care about how many bitcoins they get from each new Bitcoin block found from mining. Bitcoin miners mostly don't hold bitcoin as long term investors but they quickly cash out their bitcoins for paying mining bills (electricity, maintenance cost, staff wage, and other costs).

This means if they get enough $ from bitcoin they get each block, they will have a profitable mining business and they will not shut down their ASICs or switch them to AI data centers.

[Frankolala]

The longer the time, the higher the price of bitcoin and mining fee increases overtime. This means that in 2140, bitcoin will be very expensive and same with the mining fee and that will be enough for miners. However, I don't think that we should worry about that because none of us here will be alive to witness what will happen in 2140.

[Alphakilo]

Do you know that miners are generating more on fees now than before?

The money generated on fees before 2020 were significantly below a billion United States dollars, but starting from 2021, miners generated more fees more than a billion United States dollars.

2023/2024 were the highest with a sharp decline in 2025, but still higher than the amount generated in 2022.

I guess this statistics shows that users are up to the task of paying bigger fees for block space under certain real conditions, but the spike in price still remains volatile for now because of the decline in 2025 shown and must therefore become steadier before subsidy drops again, because what matters for Bitcoin is if the transaction fees can grow fast enough to be a replacement for block subsidy and therefore fund network security before it is exhausted.

[SquirrelJulietGarden]

I guess this statistics shows that users are up to the task of paying bigger fees for block space under certain real conditions, but the spike in price still remains volatile for now because of the decline in 2025 shown and must therefore become steadier before subsidy drops again, because what matters for Bitcoin is if the transaction fees can grow fast enough to be a replacement for block subsidy and therefore fund network security before it is exhausted.

Bitcoin price needs to rise higher and makes Bitcoin transaction fees more valuable in the future, in coming years, in upcoming market cycles. If Bitcoin price continues to rise more, Bitcoin miners will still have enough money from mining, and getting rewards from block subsidy and transaction fees. When Bitcoin block subsidy will be halved more and more in coming halving cycles, I believe it will come to a cycle with bitcoin transaction fee is bigger than block subsidy.

Generally if total block reward (a plus of block subsidy and transaction fees) is good enough, profitable enough for miners, miners will stay and not move to any other PoW blockchain or AIs.

[gwestcot]

The longer the time, the higher the price of bitcoin and mining fee increases overtime. This means that in 2140, bitcoin will be very expensive and same with the mining fee and that will be enough for miners. However, I don't think that we should worry about that because none of us here will be alive to witness what will happen in 2140.

It is not enough to offset the loss of a block reward. Fees can only go up so high before people stop using it altogether. Fees, cumulatively, can only go so high on a fixed block size. The whole system will collapse in maybe 2 cycles if the price doesn't move fast. Tradfi has now sunk their teeth into Bitcoin. The price can be controlled, to a degree, via futures and other financial instruments. I knew it was cooked the moment people started celebrating tradfi participation in the ecosystem.  

[X-ray]

One thing that I know is from the appreciation of the price.

The total supply is capped and there is Bitcoin lost over time that'll increase scarcity and when Bitcoin's price is high, the transaction fee will be enough.

From the data, lately in every halving, bitcoin will have a bullrun and the value go up 2x from previous cycle's high or even more which we know as bullrun cycle.

So, the market knows that with every halving the value of bitcoin will increase because less emission.

At the end of the day we're talking about 100+ years into the future, by then there might be better solution.

[Darker45]

Who pays "when the block reward is almost gone?" It's still mainly the block reward and transaction fees. If it's not worth it, then some will leave. Those who remain might find the endeavor worth it with much of the competition gone. If it's still losing, they'd also leave. This will incentivize more and more those who remain. And with the difficulty going lower and lower, potential players might be enticed to join.

Also, I remember miners recycling the heat coming from the rigs into good use like heating homes, greenhouses, and the like. Depending on the scale, these could be monetized as well.

Actually, if you take a look at some mining companies, they have revenues outside the block reward and fees. Some are even earning from selling power back to the grid.

[pooya87]

Everyone here knows the block reward gets cut in half about every four years, and most people see the halving as a good thing for the price, but here is the thing, I think the more important question is what happens to security when the subsidy becomes small. Right now miners are paid mostly by the new coins in each block, and fees are only a small part of that.

Block halving is not important for the price, it is important for having a controlled supply of a money that is supposed to have a capped supply: https://en.bitcoin.it/wiki/Controlled_supply

And when you talk about miners being "paid" you have their cost in mind and that cost of operations is being calculated in fiat not in bitcoin. For example they pay their electricity bill, pay their employees, pay server costs, maintenance, taxes, etc. all in fiat so you have to consider the fiat value not the bitcoin amount.
For example back in 2017 the miners were being paid 12.5BTC per block which was barely $1000 so the total income was $12,500 but today they are being paid 3.125BTC per block and the average has been around $70k which means $218,750.

In other words with 2 halvings and with miners' reward being cut by half twice they are being "paid" 1650% more money.

In the far away future when the subsidy is even smaller, two things will cover their costs: (1) the value of bitcoin having gone up (2) the fees.