As of May 31, 2023, USDC is fully backed by US Treasury Bills (79%), and cash deposits (18%) in fully segregated accounts.
For off-chain collateral, we rank storage methods as follows (highest to lowest)
With regulated custodians not in off-shore jurisdictions
With regulated custodians in off-shore jurisdictions (e.g, BVI, Bahamas)
Others / Undisclosed
USDC's reserves are held by BNY Mellon in the USA.
All customer assets in USDC’s reserves are fully segregated from Circle’s corporate treasury. However, Circle's claim of USDC being bankruptcy-remote is yet to be proven.