Segregated Witness or SegWit is a soft work protocol that changes the method of storing data. It was presented in December 2015 by Pieter Wiulle as a solution to Bitcoin’s scalability problems.
The core concept of SegWit is a segregation of the digital signature from the transactions data. As the digital signature is 65 percent of transaction, removing it from the data will increase Bitcoin’s blockchain maximum size from 1MB to a little under 4MB. SegWit could also help with fixing a bug called “transaction malleability,” which is when anyone could change some small details and modify the transaction ID. This bug prevented the development of new features for Bitcoin.
Segregated Witness was activated on August 24, 2017. Still, not everyone who accepts SegWit as Bitcoin can still work using the old protocol. Only around 30 percent of transactions are using a new format at the day of writing this article.