The ERC-8021 proposal aims to integrate 'builder codes' into Ethereum, inspired by their success on platforms like Hyperliquid and Polymarket. These codes function as referral tools, allowing app developers to earn revenue by driving transaction volume. For instance, Phantom has reportedly generated nearly $100,000 daily in trading revenue using Hyperliquid's builder codes. The proposal suggests adding a transaction suffix and a code registry to standardize this system. Hyperliquid's builder codes have already facilitated $40 million in developer revenue and over $100 billion in trading volume.