Bitcoin Forum

Bitcoin => Development & Technical Discussion => Topic started by: K210 on November 23, 2017, 12:32:15 PM

Title: What is the current max block size?
Post by: K210 on November 23, 2017, 12:32:15 PM
I've been away from bitcoin for a while and just checked a bitcoin block explorer to find blocks larger than 1MB. Has the maximum block size been raised or has this got something to do with segwit? Also if the max block size has gone up what is it now?

Title: Re: What is the current max block size?
Post by: Colorblind on November 23, 2017, 01:11:16 PM

So How Big Can Segwit Blocks Get?
Blocks received by legacy nodes will be less than 1,000,000 bytes. Blocks received by Segwit nodes, on the other hand, can be bigger, but how much bigger?
It turns out that if you made a pathologically large Segwit transaction, you can make a block with just the coinbase transaction and a pathologically large Segwit transaction that’s very close to 4MB. Essentially, this pathologically large Segwit transaction would be mostly Witness Data with the block weight just under 4,000,000. That block would be very close to 4MB, but way under 1,000,000 bytes when stripped of witness data. This is an extraordinary case and wouldn’t be very profitable for a miner unless that transaction also had an extraordinarily high fee.
The normal case without pathologically large/giant fee Segwit transactions results in a block size of around 2MB, which is what the creators of Segwit designed for. When you hear someone say “Segwit is a block size increase”, this is what they’re referring to. The average Segwit block size will be roughly 2MB, though Legacy nodes will still receive blocks that are 1,000,000 bytes or lower due to stripped witness data.