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19 votes
Accepted

Why is coinbase mentioned in a BIP?

The coinbase mentioned in BIP34 is not the company; it is referring to the first transaction in a Bitcoin block (which is special as it is allowed to bring new currency into circulation). Coinbase-the-...
Pieter Wuille's user avatar
14 votes
Accepted

Why do miners seem to be using consecutive letters for the Coinbase transaction text?

According to BIP 34 the coinbase transaction is required to start with the block height. The format is a single byte giving the count of bytes to follow (currently 3) and then the block height in ...
Nate Eldredge's user avatar
11 votes

What is the coinbase?

David has already given a good explanation of the term coinbase, but I'd like to give further details on the coinbase transaction. The coinbase transaction is a special type of transaction. Every ...
Murch's user avatar
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11 votes
Accepted

Why would a miner put an OP_RETURN in a coinbase transaction?

Every segwit block has one such OP_RETURN in the coinbase transaction: It's the Merkle root of the witness tree. When the segwit softfork was activated, this included a fix to the third-party ...
Murch's user avatar
  • 75.9k
10 votes
Accepted

Why are there more than two transaction outputs in a coinbase transaction?

A coinbase transaction can have as many outputs as the miner who created it wants. You may see that there are not just one output for the reward, sometimes there are multiple outputs so that the ...
Ava Chow's user avatar
  • 70.9k
10 votes
Accepted

What is the Block 1,983,702 Problem?

Bitcoin assumes a (txid, vout) pair, usually referred to as an "outpoint", is a unique identifier for a UTxO. This assumption did not actually hold in the early years of Bitcoin, since two ...
Antoine Poinsot's user avatar
9 votes

Why does this coinbase transaction have two op_return outputs?

Coinbase transactions have some special rules not shared by other transactions: only one per block must be the first transaction in the block must have OP_RETURN output with witness commitment if ...
Murch's user avatar
  • 75.9k
9 votes
Accepted

Will a post-subsidy block with no transactions include a coinbase transaction?

Every Bitcoin block is required to have a coinbase transaction, regardless of fees or subsidy. Additionally, every transaction (including the coinbase), must have at least one output (possibly 0-...
Pieter Wuille's user avatar
8 votes
Accepted

Why does IsCoinBase() check if there is exactly one input?

A coinbase transaction is not allowed to have any other inputs, hence this check. Furthermore, because this check is part of consensus code, it is the definition for a coinbase transaction, so this ...
Ava Chow's user avatar
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8 votes
Accepted

Does the coinbase transaction have inputs?

Coinbase transactions must: Have exactly 1 input. That input must have prevout hash 0000...0000, and index 0xFFFFFFFF (an output which isn't actually spent). The input's scriptSig must be between 2 ...
Pieter Wuille's user avatar
7 votes
Accepted

Why does Bitcoin block 526,591 have a 6.25 (instead of 12.5) block reward?

There is a maximum limit on the block reward which is 12.5 BTC but nothing prevents a miner from claiming less than 12.5 BTC. In fact, there have been times when miners forgot to claim any bitcoin at ...
Pedro's user avatar
  • 753
7 votes
Accepted

Was it always required for the Coinbase transaction to be the first transaction in a block?

This is not true. Code and code comments in v0.1.5 (the oldest tagged version in git) enforce that there always is a coinbase transaction and that it must always be the first. There cannot be a ...
Ava Chow's user avatar
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7 votes
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Is it possible for the coinbase transaction in block 164384 to be duplicated in block 1983702?

It would be possible for block 1,983,702 to repeat the coinbase transaction of block 164,384 under these three conditions: The block does not collect any segwit transactions, otherwise a witness ...
Murch's user avatar
  • 75.9k
6 votes
Accepted

How is 10% transaction fee possible for a bitcoin transfer from coinbase to another exchange?

This is normal. You can see on https://bitcoinfees.earn.com/ that BTC 0.001 is a pretty average fee right now. You should not think of it as a percentage, since the fee for a transaction is not ...
Nate Eldredge's user avatar
6 votes
Accepted

Can a coinbase transaction have a segwit output?

Other than the total value needing to be correct (no more than the block reward plus fees), the outputs of a coinbase transaction are completely unrestricted and act the same as any other transaction.
Claris's user avatar
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6 votes
Accepted

Why are miners setting the locktime in coinbase transactions?

Wang Chun of f2pool (@satofishi) said on Twitter: “We repurpose those 4 bytes to hold the stratum session data for faster reconnect.” He went on to say: "The coinbase locktime is set to: ...
bordalix's user avatar
  • 627
6 votes
Accepted

Where was the term "coinbase" first coined, who first used it?

The term "coinbase" was most likely coined by Satoshi through the IsCoinbase method of the CTransaction class. It was both part of the first publicly distributed version of the source code ...
Antoine Poinsot's user avatar
6 votes
Accepted

When was the first OP_RETURN output in a coinbase?

The first coinbase transaction that has an OP_RETURN output is in block 246816. The transaction has 288 outputs in total, and the OP_RETURN is the last one.
Vojtěch Strnad's user avatar
6 votes
Accepted

What's the smallest possible coinbase transaction / block size?

All transactions, including coinbase transactions must have at least one input and one output. since the output value is encoded in a fixed number of bytes, not claiming the block subsidy does not ...
Antoine Poinsot's user avatar
5 votes
Accepted

Orphan block payment maturity

So is it that a miner who mined an orphan block receives the outputs of coinbase transaction but can never spend them? Kind of. In such a case the number of bitcoins in circulation would reduce ...
Ava Chow's user avatar
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5 votes
Accepted

What is the maximum number of bytes the coinbase scriptSig (coinbaseaux) can hold?

The maximum is 100 bytes and is checked and defined here: https://github.com/bitcoin/bitcoin/blob/master/src/consensus/tx_verify.cpp#L195
Ava Chow's user avatar
  • 70.9k
5 votes
Accepted

Is there a maximum balance that a single address can hold?

Nope. Not 1 bit. A balance (in this context) is the sum of all UTXO's for a given address. There is no limit on the number of UTXO's or their total amount (from the perspective of how the blockchain ...
cleanmarker's user avatar
5 votes
Accepted

Some doubts regarding the structure of the Coinbase Transaction?

These are the requirements on the coinbase transaction that I am currently aware of. The transaction is structured like every other transaction, though not all fields have the same meaning. Version: ...
Pieter Wuille's user avatar
5 votes
Accepted

What is OP_RETURN b9e11b6d?

The mentioned OP_RETURN output appears to be the footprint of merged-mining VCash, a Mimblewimble-based SHA-256d coin, with Bitcoin. I discovered this via the string 0xb9e11b6d appearing in these ...
Murch's user avatar
  • 75.9k
5 votes
Accepted

Can a coinbase transaction have more than one input?

No, coinbase transactions must have exactly one input, one with a coinbase field instead of referencing a UTXO to spend. Additional inputs are not allowed. See also this related topic which describes ...
Murch's user avatar
  • 75.9k
5 votes
Accepted

Can a miner open a Lightning channel with a coinbase output?

After thinking some more about it: it would be impractical to open a channel with a coinbase output. For one, there is the maturation period for coinbase outputs. Since coinbase outputs can only be ...
Murch's user avatar
  • 75.9k
5 votes

Different balances between fullnode and bitcoin explorer

You appear to have searched for a Pay to Public Key Hash (P2PKH) address, but the output on the coinbase transaction of block 200 is a Pay to Public Key (p2pk) output. There is no address standard for ...
Murch's user avatar
  • 75.9k
5 votes
Accepted

Are all transactions, whether SegWit or non-SegWit, part of the commitment in a coinbase transaction?

The wtxids of all transactions are committed to by the witness commitment tree in the coinbase transaction (except the coinbase wtxid itself, as that would be a cyclic dependency). This includes non-...
Pieter Wuille's user avatar
5 votes

Is it possible for the coinbase transaction in block 164384 to be duplicated in block 1983702?

Yes, it is possible for block 1,983,702 to duplicate the coinbase of block 164,384 with the current consensus rules. Starting with block 1,983,702 the explicit BIP30 check will be re-enabled (see this ...
Antoine Poinsot's user avatar
4 votes

Values for txid and vout for create a coinbase transaction

The coinbase transaction contains a single input, which has txid set to 0000000000000000000000000000000000000000000000000000000000000000 and vout set to 0xFFFFFFFF.
meshcollider's user avatar
  • 11.9k

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