<blockquote>
<p><strong>could someone create millions of transactions with no fees, to congest the mempool and slow down the network?</strong></p>
</blockquote>
<p>Most nodes will discard and not relay any transactions with a fee less than their configured minimum relay transaction fee.</p>
<p>As <a href="https://en.bitcoin.it/wiki/Miner_fees" rel="nofollow noreferrer">https://en.bitcoin.it/wiki/Miner_fees</a> says</p>
<blockquote>
<h2>Relaying</h2>
<p>The reference implementation's rules for relaying transactions across the peer-to-peer network are very similar to the rules for sending transactions, as a value of 0.00001 BTC is used to determine whether or not a transaction is considered &quot;Free&quot;. However, the rule that all outputs must be 0.01 BTC or larger does not apply. To prevent &quot;penny-flooding&quot; denial-of-service attacks on the network, the reference implementation caps the number of free transactions it will relay to other nodes to (by default) 15 thousand bytes per minute.</p>
<h2>Settings</h2>
<div class="s-table-container">
<table class="s-table">
<thead>
<tr>
<th>Setting</th>
<th>Default Value (units)</th>
</tr>
</thead>
<tbody>
<tr>
<td>txconfirmtarget</td>
<td>2 (blocks)</td>
</tr>
<tr>
<td>paytxfee</td>
<td>0 (BTC/kB)</td>
</tr>
<tr>
<td>mintxfee</td>
<td>0.00001 (BTC/kB)</td>
</tr>
<tr>
<td>limitfreerelay</td>
<td>15 (thousand bytes per minute)</td>
</tr>
<tr>
<td>minrelaytxfee</td>
<td>0.00001 (BTC/kB)</td>
</tr>
<tr>
<td>blockmaxsize</td>
<td>750000 (bytes)</td>
</tr>
<tr>
<td>blockminsize</td>
<td>0 (bytes)</td>
</tr>
<tr>
<td>blockprioritysize</td>
<td>0 (bytes)</td>
</tr>
</tbody>
</table>
</div></blockquote>
<p>So there already are countermeasures to denial of service attacks .</p>
<p>None of this has anything to do with mining rewards. I don't doubt miners will also ruthlessly prune any transactions that don't serve to maximise their profits.</p>

CC BY-SA 4.0
2021-09-08T10:41:08.043Z
2021-09-08T10:54:43.590Z
2021-09-08T10:54:43.590Z
RedGrittyBrick
<p>After mining rewards go down to 0, it is possible miners will not pick up transactions with 0 fees. In that case, could someone create millions of transactions with no fees, to congest the mempool and slow down the network?</p>

CC BY-SA 4.0
2021-09-07T22:19:04.063Z
The answer to your question is no (I'll write an actual answer latee to explain), but just to know what I have to focus on: why do you think mining rewards have anything to do with this?
Pieter Wuille
CC BY-SA 4.0
2021-09-08T06:08:18.757Z
This is not a change in the future; already today, and for a long time, miners usually prefer higher-fee txns, unless you or someone incentivizes some miner(s) out-of-band. This is why wallets automatically suggest (or simply use) a fee rate based on recent successful txns. See as Stack already suggested https://bitcoin.stackexchange.com/questions/69030/how-did-these-zero-transaction-fee-transactions-make-it-into-the-bitcoin-network
dave_thompson_085
CC BY-SA 4.0
2021-09-10T21:42:06.017Z
@PieterWuille the reason mining reward going down to 0 was relevant to this question...is because without mining reward and transaction fee, the transaction has no incentive left and thus likely won't be picked up by any miner.
septerr
<bitcoin-core><transaction-fees><mempool>
After mining rewards go down to 0, can someone clog the Bitcoin network by creating millions of transactions with no fees?
septerr
# After mining rewards go down to 0, can someone clog the Bitcoin network by creating millions of transactions with no fees?

(Asked by: username_0 on 2021-09-07)

After mining rewards go down to 0, it is possible miners will not pick up transactions with 0 fees. In that case, could someone create millions of transactions with no fees, to congest the mempool and slow down the network?

**Tags:** bitcoin-core, transaction-fees, mempool

> **Comments:**
> **username_1**: The answer to your question is no (I'll write an actual answer latee to explain), but just to know what I have to focus on: why do you think mining rewards have anything to do with this?  
> **username_2**: This is not a change in the future; already today, and for a long time, miners usually prefer higher-fee txns, unless you or someone incentivizes some miner(s) out-of-band. This is why wallets automatically suggest (or simply use) a fee rate based on recent successful txns. See as Stack already suggested https://bitcoin.stackexchange.com/questions/69030/how-did-these-zero-transaction-fee-transactions-make-it-into-the-bitcoin-network  
> **username_0**: @username_1 the reason mining reward going down to 0 was relevant to this question...is because without mining reward and transaction fee, the transaction has no incentive left and thus likely won't be picked up by any miner.  

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## 1 answers

### Answer by username_3 on 2021-09-08. Score: 3 | Accepted answer

> **could someone create millions of transactions with no fees, to congest the mempool and slow down the network?**

Most nodes will discard and not relay any transactions with a fee less than their configured minimum relay transaction fee.

As <https://en.bitcoin.it/wiki/Miner_fees> says

> ## Relaying
>
> The reference implementation's rules for relaying transactions across the peer-to-peer network are very similar to the rules for sending transactions, as a value of 0.00001 BTC is used to determine whether or not a transaction is considered "Free". However, the rule that all outputs must be 0.01 BTC or larger does not apply. To prevent "penny-flooding" denial-of-service attacks on the network, the reference implementation caps the number of free transactions it will relay to other nodes to (by default) 15 thousand bytes per minute.
>
> ## Settings
>
> | Setting | Default Value (units) |
> | --- | --- |
> | txconfirmtarget | 2 (blocks) |
> | paytxfee | 0 (BTC/kB) |
> | mintxfee | 0.00001 (BTC/kB) |
> | limitfreerelay | 15 (thousand bytes per minute) |
> | minrelaytxfee | 0.00001 (BTC/kB) |
> | blockmaxsize | 750000 (bytes) |
> | blockminsize | 0 (bytes) |
> | blockprioritysize | 0 (bytes) |

So there already are countermeasures to denial of service attacks .

None of this has anything to do with mining rewards. I don't doubt miners will also ruthlessly prune any transactions that don't serve to maximise their profits.


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