Questions tagged [mempool]

Every node has their unique memory pool in which it tracks unconfirmed transactions. Use this tag for questions on how transactions enter and exit the mempool, how the mempool is delimited and other aspects of how it works.

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Additional instructions in TX

Would it be possibile to add additional information in TX? I would like to add time of transaction in it. Would hash of TX change if hostile node would change that time ?
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What is the purpose of indexing the mempool by these five criteria?

In the bitcoin source code in txmempool.h, a comment says that unconfirmed transactions are indexed by five criteria: * mapTx is a boost::multi_index that sorts the mempool on 5 criteria: * - ...
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Withdrawal Transaction Went to Mempool

I am very noob in bitcoin world and I have invested at one of the BTC trader. After trading and making profit I did the withdrawal transaction of rupees 5220$ And suddenly it went in pending state. ...
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Is there a way to know how many of currently unconfirmed transactions in the MemPool is currently being attempted by other miners?

Assume there there 100 unconfirmed transactions currently in the MemPool. And the size of a block is such that it's roughly made up of 10 transactions. Now when a miner completes the Proof of Work &...
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Why would users want to submit a transaction directly to a specific miner?

I am wondering why some users are interested to send their Bitcoin transactions to a specific miner? This should increase the delay because of waiting for the specific miner to win. Are there any ...
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How do transactions get into the mempool?

I was tracking a transaction using a Bitcoin Core command. I was able to extract info on whether the transaction had entered the mempool. Among the information I got were details such as "the ...
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Is taproot considered nonstandard to older clients?

When asking an older bitcoind node to broadcast a transaction which includes or spends a p2tr output, how will they respond? Will they broadcast the transaction? Will only certain bitcoind versions ...
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Does every single node in the blockchain validate the transactions in the mempool?

I have read several responses to various questions SE. Some responses partially respond to the question so I was hoping to get your help to bridge my gaps in understanding. Does every single node on ...
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How is this 0 sat tx even possible? How can I do them?

A Redditor from r/Bitcoin spotted a 0 sat/vB transaction in which the transaction occurred sometime in October last year (presumably by F2Pool). The transaction ID is as follows: ...
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Understanding Bitcoin Validator Node Decentralization

I am hoping to better understand the difference between miner nodes and validator nodes and the decentralization risks (if any) posed by one party controlling X% of all validator nodes. I have been ...
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Is there a way to know how good a miner is choosing its transanctions to be mined from a fee maximization point of view?

Well, this is the way I've tried: When a mined block arrives to my node, I compare it against a transaction selection algorithm using my mempool. (I know my mempool it's different than the miner's one,...
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If we allow zero fee transactions within new policy rules for package relay why not also allow zero satoshi outputs?

In the proposed package relay the requirement that a transaction must meet the minimum relay fee rate is relaxed (the fee rate can be zero by the new policy rules) as long as the package in its ...
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How to fetch the last month's block and transactions from mempool?

I want to fetch last month's block and transactions from mempool using typescript. And then persist this to MongoDb. In mempool API-REST there is a code of "GET_Block". import mempoolJS from ...
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Validate raw transaction hex without broadcasting

I would like to check the validity of a raw transaction (i.e. whether it would be accepted by network nodes), without broadcasting the transaction to the network. I am interested in knowing what is ...
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Why is a synchronized mempool necessary in the network?

My understanding is that nodes maintain a mempool of unexecuted transactions. They use a bloom filter to query other nodes for transactions they do not currently have in their own mempool... thus ...
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Huge dependency graphs for transactions in mempool

I'm creating a web page to monitor bitcoin mempool https://mempoolexplorer.com/ and I've realized that sometimes exists huge transactions dependency graphs in the mempool. I'm talking about +-700 ...
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Connection Reset after sending mempool message

I build a python script to talk to bitcoin test nodes. When I'm sending mempool messages, my connection is getting is reset. Also sometimes when connecting to Jimmy Song's testnet node (testnet....
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Why does Bitcoin Core store the block height and the time of each transaction in the memory pool?

...given that one can be derived from the other? Surely the unsigned integer of height would be sufficient without the addition uint64_t of the time (to the second), wouldn't it?
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After mining rewards go down to 0, can someone clog the Bitcoin network by creating millions of transactions with no fees?

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 ...
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Error 400 when pushing tx hex to mempool.space's API

I am using the code syntax provided by mempool.space for a POST transaction request from their website here: https://mempool.space/api const mempoolJS = require("@mempool/mempool.js") const ...
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Is the `mempool` message reliable?

According to https://github.com/bitcoin/bitcoin/blob/master/src/net_processing.cpp#L3775-L3801, it seems like the mempool message is only responded to in certain cases. Can someone help understand how ...
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Unbroadcast count doesn't change as expected after 15 minutes

Related question: Test that mempool reattempts delivery of locally submitted transaction I tried running hidden RPC mockscheduler, I think it worked that day after relaunching nodes few times and ...
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Test that mempool reattempts delivery of locally submitted transaction

Test: https://github.com/bitcoin/bitcoin/blob/master/test/functional/mempool_unbroadcast.py I am trying this manually with below steps: Run two nodes (regtest): Node1: bitcoind -port=18333 -rpcport=...
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Reorgs and MEV in Bitcoin

Recently one of the altcoin that has lot of other issues is in news because of MEV (Miner Extractable Value). Honestly I don't care if someone exploits it or it affects the altcoin in any other way. ...
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Making regtest's generatetoaddress work with blocksonly=1

I'm setting up a regtest scenario in which I want to send transactions which should be included in new blocks created via the generatetoaddress RPC call. However, I want to disable transaction ...
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Can I transfer some BTC with 0 tx fee now, when the mempool is empty?

I wanna send a tiny amount of BTC (0.001BTC). I am not in a hurry and I noticed the mempool is sometimes empty these days because the market is cold. So can I set the network fee to 1sat/byte or even ...
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What happens if nSequence is set to 0x00000000?

I know setting nSequence 0x00000001 means the transaction is not valid until 1 block has elapsed since its's prevout confirms. At most one spend per two blocks. What happens if it's set to 0x00000000? ...
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A question about CPFP relaying policy

Let's say I broadcast a transaction tx0 signaling RBF replaceability. Later on, send another transaction tx1 that spends the same inputs of tx0, but this time with higher fees. In this case, tx0 is ...
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what happens to low-fee or forgotten transactions

If a transaction has a fee that is too low then it is possible for the transaction to either age out of the mempool (14 days) or get removed because the mempool reaches its max size. So what happens ...
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How to save the mempool information immediately before the node receives a block?

I want to use Bitcoin RPC API 'getrawmempool' to save the snapshot of the mempool immediately before my full node receives a block. This requires modification of the Bitcoin source code. How should I ...
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How are txns sorted correctly in Merkle trees between nodes and validated via Proof of Work

I am interested in exactly what happens to transactions in the pending block (block that is being mined at the time). From what I understand, transactions are the stored as a Merkle tree hash inside ...
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Why does the mined block differ so much from the block template?

I am looking at the specific block at height 680175. At the time when the block was not mined yet, I received the block template via bitcoin-cli getblocktemplate '{"rules": ["segwit&...
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Miner's pool and Mempool relationship

I am wondering why we need Mempool (central and aggregated pool) while each miner has its own pool? If we need the Mempool as an architectural design, how we can make sure that miners are sending ...
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How can an output be spent while the transaction is in mempool

I have seen transactions on a block explorer where the transaction is in mempool (unconfirmed) but one of the outputs already appears as spent, I am curious how this works. This question is a ...
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What is the difference between the txsize in mempool and mempool dynamic usage?

There is a table for the txsize in mempool and dynamic memory usage of mempool on statoshi.info's mempool overview? The default size of mempool defined in Bitcoin is 300MB, so is this default size the ...
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Where can I get a list of stale RBF'd transactions?

I would like to prove that a certain transaction was in the mempool on a certain date before it got replaced via RBF with another transaction. Is there any service that provides this data?
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Trying to understand the mempool and how transactions are picked

I am very new to blockchain and try to understand it completely. What I think I understood is, that every transaction is going to the mempool first and these transactions are getting picked by miners. ...
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Does my node rebroadcast its mempool transactions on startup?

Say my node has transactions in its mempool and then gets shut down and restarted. Does it save the mempool to disk and reload this mempool when it starts back up, or does its mempool get lost on ...
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Will nodes configured with a larger-than-default mempool automatically retransmit transactions that have been dropped from the default mempool?

If a transaction is sent and dropped from the default mempool before it is included in a block, but nodes with a larger-than-default mempool size exist that still have the transaction, will those ...
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Bitcoin transaction failed to broadcast (code 66)

I am using bitcoind. I got this error while trying to send a transaction: CommitTransaction(): Transaction cannot be broadcast immediately, mempool min fee not met, 6835 < 7865 (code 66) The ...
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What unconfirmed transactions in Mempool get into a block? [duplicate]

I have a question regarding picking unconfirmed transactions from the mempool. Let's say, there are 1000 transactions in the mempool. Can I randomly select some transactions, say, transaction a, b, c, ...
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Where in ~/.bitcoin are mempool and UTXO pools written?

Where in ~/.bitcoin are the two pools in question stored when their size grows above the size set by dbcache and maxmempool in bitcoin.conf. Is UTXO pool written to such location at Bitcoin Core's ...
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Do miners mine their own transactions or submit them to the network?

I am wondering how miners are behaving toward their own transactions. Do they send their own transactions to the mempool or can they process/confirm them directly? I am assuming that the miners are ...
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How to choose the transactions for a block?

From my understanding, the memory pool (or transaction pool) contains "open" or "unconfirmed" transactions that have to be validated and can be chosen (arbitrarily?) to be part of ...
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Unconfirmed transaction for 6 days now. need assistance for using CPFP

I have an unconfirmed transaction that has been sitting there for 6 days now. The fees only got higher sins i've made the transaction and i do not feel comfortabel waiting. I'm unable to use RBF sins ...
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Why are the drops in mempool unconfirmed transaction count not of constant height?

I was just browsing the following mempool visualization and couldn't come up with a good explanation why the drops in unconfirmed transaction count are not of pretty much constant height but vary ...
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What is the network mempools unconfirmed transaction expiration time?

I sent a bare $1000 multisig transaction using sendrawtransaction with a too low fee. When I create a new transaction with a higher fee, I m getting txn-mempool-conflict error, and when I use the ...
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Why can't default minimum fee rate be changed to 0.1-0.2 sat/vByte?

Main question (focus on this incase you are looking to close it as "needs focus"): Why can't we change default minimum fee rate to something below 1 sat/vByte? It was done in past: https://...
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Which tool can I use to calculate the best fee for a specific time?

Let's say I'm okay with a transaction to be included in a block in about 24h. The fee is obviously dependent on the network congestion. Which (online) tools can I use to calculate the optimal fee ...
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What is the difference between policy and consensus when it comes to a Bitcoin Core node validating scripts?

What is the difference between policy and consensus when it comes to a Bitcoin Core node validating transaction scripts? Can you give some examples of checks that are considered policy and checks that ...
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