How can I view 0x644bb8a4's crypto portfolio?

You can view the full portfolio of 0x644bb8a4 (0x644b68ca3ce3d3f538ac0d85f81547bbeb54b8a4) on Zerion at https://app.zerion.io/0x644b68ca3ce3d3f538ac0d85f81547bbeb54b8a4/overview — including token balances, DeFi positions, NFTs, and transaction history across 20+ chains.

How can I access wallet portfolio data programmatically?

Use the Zerion API at https://developers.zerion.io to query any wallet's portfolio, token positions, DeFi positions, NFTs, and transaction history programmatically.