What is SegWit?

How do you fit more transactions into Bitcoin without dropping any security checks?

Segregated Witness means a “separated witness.” The “witness” here is the data proving that certain bitcoin may be spent, mainly the digital signatures. SegWit places this data in a separate part of the transaction. The signatures aren’t deleted or moved off the blockchain. They remain available for verification.

Picture an envelope with a payment order and its signed supporting documents. Instead of treating everything as one package, the order and the documents are organized separately. In Bitcoin, though, there’s an extra change: signature data counts with less weight toward the block’s capacity limit. So, depending on the kind of transactions, more of them can fit.

Why it matters

If you send bitcoin, the practical benefit is that a transaction spending bitcoin from a SegWit address usually takes up less billable space than an equivalent legacy one. That can mean a lower network fee, but not a guaranteed cheap or instant transfer. Congestion and the fee you choose still matter.

SegWit also addresses transaction malleability: the possibility of changing a transaction’s ID by altering the signature data, without changing the payment. This fix helped the development of the Lightning Network, where transactions need stable IDs.

It was deployed as a soft fork, i.e. a rule upgrade that remains compatible with older nodes. We find this combination especially useful: better use of the available space and a technical foundation for additional features.

What to watch out for

In a wallet you may come across the “Native SegWit” option, with Bitcoin addresses starting with bc1q. It isn’t a different coin or a different network. Before a withdrawal, check that the sending service supports that address type. Also, an exchange’s withdrawal fee isn’t necessarily the same as the actual network fee of the transaction.