Coinbase Custody is the largest operator of a Tezos staking validator, despite charging higher fees.
The firm is staking over 65 million XTZ as of March 30, according to research conducted by The Block's John Dantoni. Coinbase Custody launched its staking service in April 2019. That equates to more than $110 million at today's XTZ price of roughly $1.67.
Coinbase is followed by Kraken and Binance in terms of staking service providers. Together, they constitute the "Big 3" staking exchanges and account for 19% of all XTZ that is currently being staked.
As Dantoni noted, the Coinbase's XTZ staking service first went live, it was comparatively small when seen alongside Cryptium Labs, which had been in operating for the previous nine months. At one point, Polychain Labs (which is not included in the graph above) was the largest validator on the network before Coinbase surpassed it in mid-December.
Coinbase generated 1187% more XTZ in Q2 2019, 601% more in Q3, and 139% more in Q4. By Q1 2020, Coinbase's validator had grown larger than Cryptium Labs and generated 86% more XTZ.
Coinbase charges the highest fee –25% – for XTZ staking, while Kraken charges 7.25% and Binance currently charges no fee.