ghash.io

GHash.IO was a Bitcoin mining pool operated as a subsidiary of the cryptocurrency exchange CEX.IO. Founded in July 2013, it offered Bitcoin and altcoin mining services and, for a period in 2014, attracted notable attention for approaching or surpassing 50% of the Bitcoin network’s hashing power before steps were taken to reduce its share. The pool officially shut down in October 2016, with CEX.IO continuing to function as a separate platform. (en.bitcoin.it)