0

Using this post to define the format of a transaction: Create Output with a bunch of input

Why is the previous utxo index (also called the previous output index) 4 bytes?

The maximum output index should be equivalent to the maximum number of outputs that could fit into a transaction which would be constrained by block size. So is 2 bytes not enough? (2 bytes --> max index of 65,535)

Which mined transaction on mainnet has created the highest number of outputs so far?

What is the largest previous output index that has been mined into a block so far?

Related code: https://github.com/bitcoin/bitcoin/blob/master/src/primitives/transaction.h#L30

Related question: Maximum number of inputs per transaction

1
  • I think one question was not answered. Few transactions with 20000 inputs were mined in 2015. Example: 5f4d2593c859833db2e2d25c672a46e98f7f8564b991af9642a8b37e88af62bc
    – Prayank
    Dec 2 '21 at 8:13
1

In theory, a block can contain about 111000 outputs, as outputs can be as small as 9 bytes.

Still, the current 4000000 block weight limit, as well as the 1000000 block size limit that predated it, were both introduced after the transaction serialization format.

Presumably 4 bytes was just some sort of standard choice for serializing integers. Something similar in the other direction happened would timestamps I think; they are also 4 bytes, but probably should have been larger (or less accurate).

1

Realistically you're probably never going to need more than 2 bytes to represent an output index, but many of the constraints in Bitcoin aren't necessarily that closely defined to their theoretical limits. It could have been represented as a variable length integer as with other values to save a few bytes per output, but it just isn't.

Which mined transaction on mainnet has created the highest number of outputs so far?

The record for most outputs in a transaction is 13107 in 445KiB mined in 2016.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.