19 votes

Is there a difference between bytes and virtual bytes (vbytes)?

Yes, they are referring to two different metrics: size and virtual size (vsize). The size in [bytes] of a transaction refers to the raw byte length of its serialized format. It is used to measure the ...
  • 65.4k
15 votes
Accepted

How does SegWit reduce transaction size, when the signature is simply moved to another part of the transaction?

TL;DR: SegWit does not reduce the transaction size, if you're referring to the raw byte length of transactions. Instead it introduces block weight as a new metric that does not directly correspond to ...
  • 65.4k
8 votes

Is there a difference between bytes and virtual bytes (vbytes)?

For non-segwit transactions, vbytes = bytes. With the implementation of SegWit, we now see the weight of the block/transactions rather than seeing the absolute size on the wire. While calculating the ...
  • 7,028
6 votes
Accepted

Why does BIP141 define both virtual transaction size and weight?

The transaction limit under segwit is derived solely from the transaction weight and the block weight limit of 4,000,000 weight units. Virtual transaction size was not used for the limit calculation ...
  • 65.4k
6 votes
Accepted

What happens if "transaction size" is larger than "maximum block size"?

what happens if size of a transaction is larger than maximum block size? Then the transaction can never be included in a block. There is no mechanism for dividing it up into multiple blocks, or ...
  • 17.5k
5 votes

What happens if "transaction size" is larger than "maximum block size"?

Nick Odell answers the original question: The maximum transaction size is the size of the block. Source. and Transactions larger than 100 kilobytes (including witness at a 75% discount rate) ...
5 votes
Accepted

Is it possible for the `size` and `vsize` to be the same for a valid segwit (bech32) transaction?

With segwit outputs, yes. Segwit outputs do not have a witness that could get discounted. With segwit inputs, in theory possibly, but in practice no. Every standard segwit input today has a non-empty ...
5 votes
Accepted

what is measured in units of sat/kw?

I assume that James is using "sat/kw", to refer to "satoshi per kiloweightunit" as a means to express the fee rate of a transaction. "Weight" here refers to what replaced "blocksize" as a blockspace ...
  • 65.4k
4 votes
Accepted

Concept of Block weight and segwit are still unclear

Have a look: https://blockchair.com/bitcoin/block/0000000000000000000cbbceb342e07071f9621607e044ec909aa86fcdf88e8a Size = 1,158,038 bytes Weight units = 3,992,825 WU Now what does it mean? So the ...
  • 1,024
4 votes
Accepted

On chain cost of Segwit version 1 versus version 0

In general, Segwit v1 is cheaper than segwit v0 to spend but slightly more expensive to create. Segwit v1 output scripts as defined by the proposed taproot BIP will always be 35 bytes in length. ...
  • 63.3k
4 votes
Accepted

What is block weight and how is it different from block size?

Block weight is defined in BIP 141 itself: Block weight is defined as Base size * 3 + Total size. (rationale[3]) Base size is the block size in bytes with the original transaction ...
4 votes
Accepted

Different fee rate units - sat/vB, sat perkw, sat perkb

No, one vbyte [vB] is equal to four weightunits [wu]. The people working on C-Lightning use "sipa" interchangeably for a weightunit. 1,000 sat/kvB = 1 sat/vB 1 sat/vB = 0.25 sat/wu 0.25 sat/...
  • 65.4k
4 votes

Does the transaction fee depend on the transferred amount?

No. Fees depend on the size of the transaction (measured in bytes), and can start at 1 satoshi per byte. So. if your transaction weighs 400 bytes, at 1 sat / byte you’ll pay 400 sats. The size of the ...
  • 186
3 votes
Accepted

What is the current maximum Bitcoin block size in MB?

Effectively, the theoretical maximum size is 3999997B although in practice this limit cannot be reached. In Bitcoin Core v0.15.1 the default value for blockmaxweight in block creation is 3996000B. ...
  • 3,146
3 votes
Accepted

Why does the Segwit developer guide recommend to estimate fees on basis of vsize instead of weight?

The advantage of using vsize is that it is a smooth transition from size; every non-witness transaction has vsize equal to size. All code and infrastructure that used satoshi/byte before, will keep ...
3 votes
Accepted

How much does the weight of 2-of-3 multisignature inputs differ between P2SH and P2SH-P2WSH?

To calculate the block weight, you need to know the size in bytes of the non-witness data and the size in bytes of the witness data. With a P2SH-P2WSH input, your scriptSig will always be 36 bytes. ...
  • 63.3k
3 votes
Accepted

Do sigops count towards the block weight in SegWit?

No. The block weight is only calculated from the bytes themselves, not the sigops. Accounting for the sigops would need a hard fork, as explained by the section above the example: It is not ...
  • 63.3k
3 votes
Accepted

After Segwit Activation, what is the largest block size possible?

The maximum block size is 4,000,000 bytes (4 MB). This is because the block weight calculation is base size (in MB) * 3 + total size (in MB) = block weight (see BIP 141). Since the only units are MB, ...
  • 63.3k
3 votes

What is the weight of a block that contains no pay-to-witness scripts?

From BIP 144: If the witness is empty, the old serialization format should be used. It is illegal to encode a transaction using the extended serialization format if the witness is empty. Another way ...
3 votes
Accepted

What is the weight of a block that contains no pay-to-witness scripts?

The witness serialization format only applies to transactions that have witnesses. If a transaction does not have witnesses, then its witness serialization format is the non-witness serialization ...
  • 63.3k
2 votes

What is block weight and how is it different from block size?

It's a trick that increases the block size without breaking backwards compatibility with non-Segwit nodes. I found this article by Jimmy Song to be more helpful than trying to understand the BIP. The ...
  • 191
2 votes

How does SegWit reduce transaction size, when the signature is simply moved to another part of the transaction?

segwit IS a block size limit increase. No magic. The segwit mechanism enforces a limit on a weighted data size calculated by counting the non-sig part of a transaction as base data (weight=4) and to ...
  • 161
2 votes
Accepted

What is the maximum size for SegWit transactions?

The standardness limit in all recent Bitcoin Core versions with SegWit support is 400000 weight.
2 votes
Accepted

How much will Segwit *actually* increase bitcoin capacity for realistic transactions?

Note that the scriptSig field is not just the ECDSA signature itself (65 bytes) but also the public key in the case of a P2PKH input, or the redeem script for a P2SH input, and a couple more bytes for ...
  • 11.5k
2 votes
Accepted

Most transactions in a block

Is this the highest number of transactions in a block until now? The highest number of transactions in a block is 12239 in block 00000000000000001080e6de32add416cd6cda29f35ec9bce694fea4b964c7be at ...
  • 63.3k
2 votes
Accepted

Why is the block size so big, taking into account a relatively small number of transactions?

Why the size of the block 656143 is so big (Size: 2,337,727 bytes), taking into account a relatively small number of transactions (Number of Transactions: 84)? It contains a number of transactions ...
  • 15.2k
2 votes

Does the transaction fee depend on the transferred amount?

A Bitcoin transaction is a combination of one or more inputs and one or more outputs. Each input is itself an out put of a previous transaction. So it is not liquid. I think it is good to think of ...
1 vote

On chain cost of Segwit version 1 versus version 0

In Bitcoin Optech Newsletter #46, the costs are compared as follows: Overall, this makes the cost to create and spend a Taproot single-sig output about 5% more expensive than P2WPKH. ...
  • 1,024
1 vote
Accepted

Can SegWit block weight be increased without a hard fork?

The explicit block weight limit cannot be changed without a hard fork.
  • 63.3k
1 vote

How much does the weight of 2-of-3 multisignature inputs differ between P2SH and P2SH-P2WSH?

The differences between P2SH, P2SH-P2WSH and P2WSH are the following: P2SH: the scriptPubKey has a P2SH program. The scriptSig provides the corresponding script arguments and redeemscript to satisfy ...
  • 65.4k

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