As part of our continuous improvements to the BitMEX platform, at approximately 04:20:00 UTC on 15 July 2021, the following metadata on the partial action will change on the orderBookL2 and orderBookL2_25 feeds: - keys - attributes This change only affects websocket users – please update your applications if you currently use these fields on the websocket. We will make the same change in Testnet as of 14 July 2021 at approximately 04:20:00 UTC. Should you have any questions, please contact Support.