Litecoin became the first of the top 5 (by market cap) cryptocurrencies to adopt Segregated Witness.
The formal title “Segregated Witness (Consensus layer)” had Bitcoin Improvement Proposal number BIP141. The declared purpose was to prevent nonintentional bitcoin transaction malleability, allow optional data transmission, and to bypass certain protocol restrictions (such as the block size limit) with a soft fork.
It was also intended to mitigate a blockchain size limitation problem that reduces bitcoin transaction speed. It does this by splitting the transaction into two segments, removing the unlocking signature (“witness” data) from the original portion and appending it as a separate structure at the end. The original section would continue to hold the sender and receiver data, and the new “witness” structure would contain scripts and signatures. The original data segment would be counted normally, but the “witness” segment would, in effect, be counted as a quarter of its real size.
Later in May of the same year, the first Lightning Network transaction was completed through Litecoin, transferring 0.00000001 LTC from Zürich to San Francisco in under one second.